fe4b3e591b
Explain the difference (well, one of the differences) between a tag and a branch. Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
1989 lines
68 KiB
Plaintext
1989 lines
68 KiB
Plaintext
Git User's Manual
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_________________
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This manual is designed to be readable by someone with basic unix
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commandline skills, but no previous knowledge of git.
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Chapter 1 gives a brief overview of git commands, without any
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explanation; you can skip to chapter 2 on a first reading.
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Chapters 2 and 3 explain how to fetch and study a project using
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git--the tools you'd need to build and test a particular version of a
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software project, to search for regressions, and so on.
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Chapter 4 explains how to do development with git, and chapter 5 how
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to share that development with others.
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Further chapters cover more specialized topics.
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Comprehensive reference documentation is available through the man
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pages. For a command such as "git clone", just use
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------------------------------------------------
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$ man git-clone
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------------------------------------------------
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Git Quick Start
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===============
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This is a quick summary of the major commands; the following chapters
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will explain how these work in more detail.
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Creating a new repository
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-------------------------
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From a tarball:
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-----------------------------------------------
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$ tar xzf project.tar.gz
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$ cd project
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$ git init
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Initialized empty Git repository in .git/
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$ git add .
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$ git commit
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-----------------------------------------------
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From a remote repository:
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-----------------------------------------------
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$ git clone git://example.com/pub/project.git
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$ cd project
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-----------------------------------------------
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Managing branches
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-----------------
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-----------------------------------------------
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$ git branch # list all branches in this repo
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$ git checkout test # switch working directory to branch "test"
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$ git branch new # create branch "new" starting at current HEAD
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$ git branch -d new # delete branch "new"
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-----------------------------------------------
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Instead of basing new branch on current HEAD (the default), use:
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-----------------------------------------------
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$ git branch new test # branch named "test"
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$ git branch new v2.6.15 # tag named v2.6.15
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$ git branch new HEAD^ # commit before the most recent
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$ git branch new HEAD^^ # commit before that
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$ git branch new test~10 # ten commits before tip of branch "test"
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-----------------------------------------------
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Create and switch to a new branch at the same time:
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-----------------------------------------------
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$ git checkout -b new v2.6.15
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-----------------------------------------------
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Update and examine branches from the repository you cloned from:
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-----------------------------------------------
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$ git fetch # update
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$ git branch -r # list
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origin/master
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origin/next
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...
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$ git branch checkout -b masterwork origin/master
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-----------------------------------------------
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Fetch a branch from a different repository, and give it a new
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name in your repository:
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-----------------------------------------------
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$ git fetch git://example.com/project.git theirbranch:mybranch
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$ git fetch git://example.com/project.git v2.6.15:mybranch
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-----------------------------------------------
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Keep a list of repositories you work with regularly:
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-----------------------------------------------
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$ git remote add example git://example.com/project.git
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$ git remote # list remote repositories
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example
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origin
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$ git remote show example # get details
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* remote example
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URL: git://example.com/project.git
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Tracked remote branches
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master next ...
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$ git fetch example # update branches from example
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$ git branch -r # list all remote branches
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-----------------------------------------------
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Exploring history
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-----------------
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-----------------------------------------------
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$ gitk # visualize and browse history
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$ git log # list all commits
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$ git log src/ # ...modifying src/
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$ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15
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$ git log master..test # ...in branch test, not in branch master
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$ git log test..master # ...in branch master, but not in test
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$ git log test...master # ...in one branch, not in both
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$ git log -S'foo()' # ...where difference contain "foo()"
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$ git log --since="2 weeks ago"
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$ git log -p # show patches as well
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$ git show # most recent commit
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$ git diff v2.6.15..v2.6.16 # diff between two tagged versions
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$ git diff v2.6.15..HEAD # diff with current head
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$ git grep "foo()" # search working directory for "foo()"
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$ git grep v2.6.15 "foo()" # search old tree for "foo()"
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$ git show v2.6.15:a.txt # look at old version of a.txt
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-----------------------------------------------
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Searching for regressions:
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$ git bisect start
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$ git bisect bad # current version is bad
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$ git bisect good v2.6.13-rc2 # last known good revision
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Bisecting: 675 revisions left to test after this
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# test here, then:
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$ git bisect good # if this revision is good, or
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$ git bisect bad # if this revision is bad.
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# repeat until done.
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-----------------------------------------------
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Making changes
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--------------
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Make sure git knows who to blame:
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------------------------------------------------
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$ cat >~/.gitconfig <<\EOF
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[user]
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name = Your Name Comes Here
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email = you@yourdomain.example.com
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EOF
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------------------------------------------------
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Select file contents to include in the next commit, then make the
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commit:
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-----------------------------------------------
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$ git add a.txt # updated file
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$ git add b.txt # new file
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$ git rm c.txt # old file
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$ git commit
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-----------------------------------------------
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Or, prepare and create the commit in one step:
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$ git commit d.txt # use latest content of d.txt
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$ git commit -a # use latest content of all tracked files
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-----------------------------------------------
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Merging
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-------
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-----------------------------------------------
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$ git merge test # merge branch "test" into the current branch
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$ git pull git://example.com/project.git master
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# fetch and merge in remote branch
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$ git pull . test # equivalent to git merge test
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-----------------------------------------------
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Sharing your changes
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--------------------
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Importing or exporting patches:
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-----------------------------------------------
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$ git format-patch origin..HEAD # format a patch for each commit
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# in HEAD but not in origin
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$ git-am mbox # import patches from the mailbox "mbox"
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-----------------------------------------------
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Fetch a branch in a different git repository, then merge into the
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current branch:
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$ git pull git://example.com/project.git theirbranch
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-----------------------------------------------
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Store the fetched branch into a local branch before merging into the
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current branch:
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$ git pull git://example.com/project.git theirbranch:mybranch
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-----------------------------------------------
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After creating commits on a local branch, update the remote
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branch with your commits:
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$ git push ssh://example.com/project.git mybranch:theirbranch
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-----------------------------------------------
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When remote and local branch are both named "test":
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$ git push ssh://example.com/project.git test
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-----------------------------------------------
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Shortcut version for a frequently used remote repository:
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$ git remote add example ssh://example.com/project.git
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$ git push example test
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-----------------------------------------------
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Repositories and Branches
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=========================
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How to get a git repository
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---------------------------
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It will be useful to have a git repository to experiment with as you
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read this manual.
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The best way to get one is by using the gitlink:git-clone[1] command
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to download a copy of an existing repository for a project that you
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are interested in. If you don't already have a project in mind, here
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are some interesting examples:
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------------------------------------------------
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# git itself (approx. 10MB download):
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$ git clone git://git.kernel.org/pub/scm/git/git.git
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# the linux kernel (approx. 150MB download):
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$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
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------------------------------------------------
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The initial clone may be time-consuming for a large project, but you
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will only need to clone once.
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The clone command creates a new directory named after the project
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("git" or "linux-2.6" in the examples above). After you cd into this
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directory, you will see that it contains a copy of the project files,
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together with a special top-level directory named ".git", which
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contains all the information about the history of the project.
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In most of the following, examples will be taken from one of the two
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repositories above.
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How to check out a different version of a project
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-------------------------------------------------
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Git is best thought of as a tool for storing the history of a
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collection of files. It stores the history as a compressed
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collection of interrelated snapshots (versions) of the project's
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contents.
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A single git repository may contain multiple branches. Each branch
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is a bookmark referencing a particular point in the project history.
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The gitlink:git-branch[1] command shows you the list of branches:
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------------------------------------------------
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$ git branch
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* master
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------------------------------------------------
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A freshly cloned repository contains a single branch, named "master",
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and the working directory contains the version of the project
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referred to by the master branch.
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Most projects also use tags. Tags, like branches, are references
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into the project's history, and can be listed using the
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gitlink:git-tag[1] command:
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------------------------------------------------
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$ git tag -l
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v2.6.11
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v2.6.11-tree
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v2.6.12
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v2.6.12-rc2
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v2.6.12-rc3
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v2.6.12-rc4
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v2.6.12-rc5
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v2.6.12-rc6
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v2.6.13
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...
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------------------------------------------------
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Tags are expected to always point at the same version of a project,
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while branches are expected to advance as development progresses.
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Create a new branch pointing to one of these versions and check it
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out using gitlink:git-checkout[1]:
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------------------------------------------------
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$ git checkout -b new v2.6.13
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------------------------------------------------
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The working directory then reflects the contents that the project had
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when it was tagged v2.6.13, and gitlink:git-branch[1] shows two
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branches, with an asterisk marking the currently checked-out branch:
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------------------------------------------------
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$ git branch
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master
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* new
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------------------------------------------------
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If you decide that you'd rather see version 2.6.17, you can modify
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the current branch to point at v2.6.17 instead, with
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------------------------------------------------
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$ git reset --hard v2.6.17
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------------------------------------------------
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Note that if the current branch was your only reference to a
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particular point in history, then resetting that branch may leave you
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with no way to find the history it used to point to; so use this
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command carefully.
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Understanding History: Commits
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------------------------------
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Every change in the history of a project is represented by a commit.
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The gitlink:git-show[1] command shows the most recent commit on the
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current branch:
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------------------------------------------------
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$ git show
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commit 2b5f6dcce5bf94b9b119e9ed8d537098ec61c3d2
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Author: Jamal Hadi Salim <hadi@cyberus.ca>
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Date: Sat Dec 2 22:22:25 2006 -0800
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[XFRM]: Fix aevent structuring to be more complete.
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aevents can not uniquely identify an SA. We break the ABI with this
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patch, but consensus is that since it is not yet utilized by any
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(known) application then it is fine (better do it now than later).
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Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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diff --git a/Documentation/networking/xfrm_sync.txt b/Documentation/networking/xfrm_sync.txt
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index 8be626f..d7aac9d 100644
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--- a/Documentation/networking/xfrm_sync.txt
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+++ b/Documentation/networking/xfrm_sync.txt
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@@ -47,10 +47,13 @@ aevent_id structure looks like:
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struct xfrm_aevent_id {
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struct xfrm_usersa_id sa_id;
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+ xfrm_address_t saddr;
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__u32 flags;
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+ __u32 reqid;
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};
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...
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------------------------------------------------
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As you can see, a commit shows who made the latest change, what they
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did, and why.
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Every commit has a 40-hexdigit id, sometimes called the "SHA1 id", shown
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on the first line of the "git show" output. You can usually refer to
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a commit by a shorter name, such as a tag or a branch name, but this
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longer id can also be useful. In particular, it is a globally unique
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name for this commit: so if you tell somebody else the SHA1 id (for
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example in email), then you are guaranteed they will see the same
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commit in their repository that you do in yours.
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Understanding history: commits, parents, and reachability
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Every commit (except the very first commit in a project) also has a
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parent commit which shows what happened before this commit.
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Following the chain of parents will eventually take you back to the
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beginning of the project.
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However, the commits do not form a simple list; git allows lines of
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development to diverge and then reconverge, and the point where two
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lines of development reconverge is called a "merge". The commit
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representing a merge can therefore have more than one parent, with
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each parent representing the most recent commit on one of the lines
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of development leading to that point.
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The best way to see how this works is using the gitlink:gitk[1]
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command; running gitk now on a git repository and looking for merge
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commits will help understand how the git organizes history.
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In the following, we say that commit X is "reachable" from commit Y
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if commit X is an ancestor of commit Y. Equivalently, you could say
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that Y is a descendent of X, or that there is a chain of parents
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leading from commit Y to commit X.
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Undestanding history: History diagrams
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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We will sometimes represent git history using diagrams like the one
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below. Commits are shown as "o", and the links between them with
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lines drawn with - / and \. Time goes left to right:
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o--o--o <-- Branch A
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/
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o--o--o <-- master
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\
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o--o--o <-- Branch B
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If we need to talk about a particular commit, the character "o" may
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be replaced with another letter or number.
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Understanding history: What is a branch?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Though we've been using the word "branch" to mean a kind of reference
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to a particular commit, the word branch is also commonly used to
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refer to the line of commits leading up to that point. In the
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example above, git may think of the branch named "A" as just a
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pointer to one particular commit, but we may refer informally to the
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line of three commits leading up to that point as all being part of
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"branch A".
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If we need to make it clear that we're just talking about the most
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recent commit on the branch, we may refer to that commit as the
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"head" of the branch.
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Manipulating branches
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---------------------
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Creating, deleting, and modifying branches is quick and easy; here's
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a summary of the commands:
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git branch::
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list all branches
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git branch <branch>::
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create a new branch named <branch>, referencing the same
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point in history as the current branch
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git branch <branch> <start-point>::
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create a new branch named <branch>, referencing
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<start-point>, which may be specified any way you like,
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including using a branch name or a tag name
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git branch -d <branch>::
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delete the branch <branch>; if the branch you are deleting
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points to a commit which is not reachable from this branch,
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this command will fail with a warning.
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git branch -D <branch>::
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even if the branch points to a commit not reachable
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from the current branch, you may know that that commit
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is still reachable from some other branch or tag. In that
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case it is safe to use this command to force git to delete
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the branch.
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git checkout <branch>::
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make the current branch <branch>, updating the working
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directory to reflect the version referenced by <branch>
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git checkout -b <new> <start-point>::
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create a new branch <new> referencing <start-point>, and
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check it out.
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It is also useful to know that the special symbol "HEAD" can always
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be used to refer to the current branch.
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Examining branches from a remote repository
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-------------------------------------------
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The "master" branch that was created at the time you cloned is a copy
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of the HEAD in the repository that you cloned from. That repository
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may also have had other branches, though, and your local repository
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keeps branches which track each of those remote branches, which you
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can view using the "-r" option to gitlink:git-branch[1]:
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------------------------------------------------
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$ git branch -r
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origin/HEAD
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origin/html
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origin/maint
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origin/man
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origin/master
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origin/next
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origin/pu
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origin/todo
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------------------------------------------------
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You cannot check out these remote-tracking branches, but you can
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examine them on a branch of your own, just as you would a tag:
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------------------------------------------------
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$ git checkout -b my-todo-copy origin/todo
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------------------------------------------------
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Note that the name "origin" is just the name that git uses by default
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to refer to the repository that you cloned from.
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[[how-git-stores-references]]
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How git stores references
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-------------------------
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Branches, remote-tracking branches, and tags are all references to
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commits. Git stores these references in the ".git" directory. Most
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of them are stored in .git/refs/:
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- branches are stored in .git/refs/heads
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- tags are stored in .git/refs/tags
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- remote-tracking branches for "origin" are stored in
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.git/refs/remotes/origin/
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If you look at one of these files you will see that they usually
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contain just the SHA1 id of a commit:
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------------------------------------------------
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$ ls .git/refs/heads/
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master
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$ cat .git/refs/heads/master
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c0f982dcf188d55db9d932a39d4ea7becaa55fed
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------------------------------------------------
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You can refer to a reference by its path relative to the .git
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directory. However, we've seen above that git will also accept
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shorter names; for example, "master" is an acceptable shortcut for
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"refs/heads/master", and "origin/master" is a shortcut for
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"refs/remotes/origin/master".
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As another useful shortcut, you can also refer to the "HEAD" of
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"origin" (or any other remote), using just the name of the remote.
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For the complete list of paths which git checks for references, and
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how it decides which to choose when there are multiple references
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with the same name, see the "SPECIFYING REVISIONS" section of
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gitlink:git-rev-parse[1].
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[[Updating-a-repository-with-git-fetch]]
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Updating a repository with git fetch
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------------------------------------
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Eventually the developer cloned from will do additional work in her
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repository, creating new commits and advancing the branches to point
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at the new commits.
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The command "git fetch", with no arguments, will update all of the
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remote-tracking branches to the latest version found in her
|
|
repository. It will not touch any of your own branches--not even the
|
|
"master" branch that was created for you on clone.
|
|
|
|
Fetching branches from other repositories
|
|
-----------------------------------------
|
|
|
|
You can also track branches from repositories other than the one you
|
|
cloned from, using gitlink:git-remote[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git remote add linux-nfs git://linux-nfs.org/pub/nfs-2.6.git
|
|
$ git fetch
|
|
* refs/remotes/linux-nfs/master: storing branch 'master' ...
|
|
commit: bf81b46
|
|
-------------------------------------------------
|
|
|
|
New remote-tracking branches will be stored under the shorthand name
|
|
that you gave "git remote add", in this case linux-nfs:
|
|
|
|
-------------------------------------------------
|
|
$ git branch -r
|
|
linux-nfs/master
|
|
origin/master
|
|
-------------------------------------------------
|
|
|
|
If you run "git fetch <remote>" later, the tracking branches for the
|
|
named <remote> will be updated.
|
|
|
|
If you examine the file .git/config, you will see that git has added
|
|
a new stanza:
|
|
|
|
-------------------------------------------------
|
|
$ cat .git/config
|
|
...
|
|
[remote "linux-nfs"]
|
|
url = git://linux-nfs.org/~bfields/git.git
|
|
fetch = +refs/heads/*:refs/remotes/linux-nfs-read/*
|
|
...
|
|
-------------------------------------------------
|
|
|
|
This is what causes git to track the remote's branches; you may
|
|
modify or delete these configuration options by editing .git/config
|
|
with a text editor.
|
|
|
|
Fetching individual branches
|
|
----------------------------
|
|
|
|
TODO: find another home for this, later on:
|
|
|
|
You can also choose to update just one branch at a time:
|
|
|
|
-------------------------------------------------
|
|
$ git fetch origin todo:refs/remotes/origin/todo
|
|
-------------------------------------------------
|
|
|
|
The first argument, "origin", just tells git to fetch from the
|
|
repository you originally cloned from. The second argument tells git
|
|
to fetch the branch named "todo" from the remote repository, and to
|
|
store it locally under the name refs/remotes/origin/todo; as we saw
|
|
above, remote-tracking branches are stored under
|
|
refs/remotes/<name-of-repository>/<name-of-branch>.
|
|
|
|
You can also fetch branches from other repositories; so
|
|
|
|
-------------------------------------------------
|
|
$ git fetch git://example.com/proj.git master:refs/remotes/example/master
|
|
-------------------------------------------------
|
|
|
|
will create a new reference named "refs/remotes/example/master" and
|
|
store in it the branch named "master" from the repository at the
|
|
given URL. If you already have a branch named
|
|
"refs/remotes/example/master", it will attempt to "fast-forward" to
|
|
the commit given by example.com's master branch. So next we explain
|
|
what a fast-forward is:
|
|
|
|
[[fast-forwards]]
|
|
Understanding git history: fast-forwards
|
|
----------------------------------------
|
|
|
|
In the previous example, when updating an existing branch, "git
|
|
fetch" checks to make sure that the most recent commit on the remote
|
|
branch is a descendant of the most recent commit on your copy of the
|
|
branch before updating your copy of the branch to point at the new
|
|
commit. Git calls this process a "fast forward".
|
|
|
|
A fast forward looks something like this:
|
|
|
|
o--o--o--o <-- old head of the branch
|
|
\
|
|
o--o--o <-- new head of the branch
|
|
|
|
|
|
In some cases it is possible that the new head will *not* actually be
|
|
a descendant of the old head. For example, the developer may have
|
|
realized she made a serious mistake, and decided to backtrack,
|
|
resulting in a situation like:
|
|
|
|
o--o--o--o--a--b <-- old head of the branch
|
|
\
|
|
o--o--o <-- new head of the branch
|
|
|
|
|
|
|
|
In this case, "git fetch" will fail, and print out a warning.
|
|
|
|
In that case, you can still force git to update to the new head, as
|
|
described in the following section. However, note that in the
|
|
situation above this may mean losing the commits labeled "a" and "b",
|
|
unless you've already created a reference of your own pointing to
|
|
them.
|
|
|
|
Forcing git fetch to do non-fast-forward updates
|
|
------------------------------------------------
|
|
|
|
If git fetch fails because the new head of a branch is not a
|
|
descendant of the old head, you may force the update with:
|
|
|
|
-------------------------------------------------
|
|
$ git fetch git://example.com/proj.git +master:refs/remotes/example/master
|
|
-------------------------------------------------
|
|
|
|
Note the addition of the "+" sign. Be aware that commits which the
|
|
old version of example/master pointed at may be lost, as we saw in
|
|
the previous section.
|
|
|
|
Configuring remote branches
|
|
---------------------------
|
|
|
|
We saw above that "origin" is just a shortcut to refer to the
|
|
repository which you originally cloned from. This information is
|
|
stored in git configuration variables, which you can see using
|
|
gitlink:git-repo-config[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git-repo-config -l
|
|
core.repositoryformatversion=0
|
|
core.filemode=true
|
|
core.logallrefupdates=true
|
|
remote.origin.url=git://git.kernel.org/pub/scm/git/git.git
|
|
remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
|
|
branch.master.remote=origin
|
|
branch.master.merge=refs/heads/master
|
|
-------------------------------------------------
|
|
|
|
If there are other repositories that you also use frequently, you can
|
|
create similar configuration options to save typing; for example,
|
|
after
|
|
|
|
-------------------------------------------------
|
|
$ git repo-config remote.example.url git://example.com/proj.git
|
|
-------------------------------------------------
|
|
|
|
then the following two commands will do the same thing:
|
|
|
|
-------------------------------------------------
|
|
$ git fetch git://example.com/proj.git master:refs/remotes/example/master
|
|
$ git fetch example master:refs/remotes/example/master
|
|
-------------------------------------------------
|
|
|
|
Even better, if you add one more option:
|
|
|
|
-------------------------------------------------
|
|
$ git repo-config remote.example.fetch master:refs/remotes/example/master
|
|
-------------------------------------------------
|
|
|
|
then the following commands will all do the same thing:
|
|
|
|
-------------------------------------------------
|
|
$ git fetch git://example.com/proj.git master:ref/remotes/example/master
|
|
$ git fetch example master:ref/remotes/example/master
|
|
$ git fetch example example/master
|
|
$ git fetch example
|
|
-------------------------------------------------
|
|
|
|
You can also add a "+" to force the update each time:
|
|
|
|
-------------------------------------------------
|
|
$ git repo-config remote.example.fetch +master:ref/remotes/example/master
|
|
-------------------------------------------------
|
|
|
|
Don't do this unless you're sure you won't mind "git fetch" possibly
|
|
throwing away commits on mybranch.
|
|
|
|
Also note that all of the above configuration can be performed by
|
|
directly editing the file .git/config instead of using
|
|
gitlink:git-repo-config[1].
|
|
|
|
See gitlink:git-repo-config[1] for more details on the configuration
|
|
options mentioned above.
|
|
|
|
Exploring git history
|
|
=====================
|
|
|
|
Git is best thought of as a tool for storing the history of a
|
|
collection of files. It does this by storing compressed snapshots of
|
|
the contents of a file heirarchy, together with "commits" which show
|
|
the relationships between these snapshots.
|
|
|
|
Git provides extremely flexible and fast tools for exploring the
|
|
history of a project.
|
|
|
|
We start with one specialized tool which is useful for finding the
|
|
commit that introduced a bug into a project.
|
|
|
|
How to use bisect to find a regression
|
|
--------------------------------------
|
|
|
|
Suppose version 2.6.18 of your project worked, but the version at
|
|
"master" crashes. Sometimes the best way to find the cause of such a
|
|
regression is to perform a brute-force search through the project's
|
|
history to find the particular commit that caused the problem. The
|
|
gitlink:git-bisect[1] command can help you do this:
|
|
|
|
-------------------------------------------------
|
|
$ git bisect start
|
|
$ git bisect good v2.6.18
|
|
$ git bisect bad master
|
|
Bisecting: 3537 revisions left to test after this
|
|
[65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]
|
|
-------------------------------------------------
|
|
|
|
If you run "git branch" at this point, you'll see that git has
|
|
temporarily moved you to a new branch named "bisect". This branch
|
|
points to a commit (with commit id 65934...) that is reachable from
|
|
v2.6.19 but not from v2.6.18. Compile and test it, and see whether
|
|
it crashes. Assume it does crash. Then:
|
|
|
|
-------------------------------------------------
|
|
$ git bisect bad
|
|
Bisecting: 1769 revisions left to test after this
|
|
[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings
|
|
-------------------------------------------------
|
|
|
|
checks out an older version. Continue like this, telling git at each
|
|
stage whether the version it gives you is good or bad, and notice
|
|
that the number of revisions left to test is cut approximately in
|
|
half each time.
|
|
|
|
After about 13 tests (in this case), it will output the commit id of
|
|
the guilty commit. You can then examine the commit with
|
|
gitlink:git-show[1], find out who wrote it, and mail them your bug
|
|
report with the commit id. Finally, run
|
|
|
|
-------------------------------------------------
|
|
$ git bisect reset
|
|
-------------------------------------------------
|
|
|
|
to return you to the branch you were on before and delete the
|
|
temporary "bisect" branch.
|
|
|
|
Note that the version which git-bisect checks out for you at each
|
|
point is just a suggestion, and you're free to try a different
|
|
version if you think it would be a good idea. For example,
|
|
occasionally you may land on a commit that broke something unrelated;
|
|
run
|
|
|
|
-------------------------------------------------
|
|
$ git bisect-visualize
|
|
-------------------------------------------------
|
|
|
|
which will run gitk and label the commit it chose with a marker that
|
|
says "bisect". Chose a safe-looking commit nearby, note its commit
|
|
id, and check it out with:
|
|
|
|
-------------------------------------------------
|
|
$ git reset --hard fb47ddb2db...
|
|
-------------------------------------------------
|
|
|
|
then test, run "bisect good" or "bisect bad" as appropriate, and
|
|
continue.
|
|
|
|
Naming commits
|
|
--------------
|
|
|
|
We have seen several ways of naming commits already:
|
|
|
|
- 40-hexdigit SHA1 id
|
|
- branch name: refers to the commit at the head of the given
|
|
branch
|
|
- tag name: refers to the commit pointed to by the given tag
|
|
(we've seen branches and tags are special cases of
|
|
<<how-git-stores-references,references>>).
|
|
- HEAD: refers to the head of the current branch
|
|
|
|
There are many more; see the "SPECIFYING REVISIONS" section of the
|
|
gitlink:git-rev-parse[1] man page for the complete list of ways to
|
|
name revisions. Some examples:
|
|
|
|
-------------------------------------------------
|
|
$ git show fb47ddb2 # the first few characters of the SHA1 id
|
|
# are usually enough to specify it uniquely
|
|
$ git show HEAD^ # the parent of the HEAD commit
|
|
$ git show HEAD^^ # the grandparent
|
|
$ git show HEAD~4 # the great-great-grandparent
|
|
-------------------------------------------------
|
|
|
|
Recall that merge commits may have more than one parent; by default,
|
|
^ and ~ follow the first parent listed in the commit, but you can
|
|
also choose:
|
|
|
|
-------------------------------------------------
|
|
$ git show HEAD^1 # show the first parent of HEAD
|
|
$ git show HEAD^2 # show the second parent of HEAD
|
|
-------------------------------------------------
|
|
|
|
In addition to HEAD, there are several other special names for
|
|
commits:
|
|
|
|
Merges (to be discussed later), as well as operations such as
|
|
git-reset, which change the currently checked-out commit, generally
|
|
set ORIG_HEAD to the value HEAD had before the current operation.
|
|
|
|
The git-fetch operation always stores the head of the last fetched
|
|
branch in FETCH_HEAD. For example, if you run git fetch without
|
|
specifying a local branch as the target of the operation
|
|
|
|
-------------------------------------------------
|
|
$ git fetch git://example.com/proj.git theirbranch
|
|
-------------------------------------------------
|
|
|
|
the fetched commits will still be available from FETCH_HEAD.
|
|
|
|
When we discuss merges we'll also see the special name MERGE_HEAD,
|
|
which refers to the other branch that we're merging in to the current
|
|
branch.
|
|
|
|
The gitlink:git-rev-parse[1] command is a low-level command that is
|
|
occasionally useful for translating some name for a commit to the SHA1 id for
|
|
that commit:
|
|
|
|
-------------------------------------------------
|
|
$ git rev-parse origin
|
|
e05db0fd4f31dde7005f075a84f96b360d05984b
|
|
-------------------------------------------------
|
|
|
|
Creating tags
|
|
-------------
|
|
|
|
We can also create a tag to refer to a particular commit; after
|
|
running
|
|
|
|
-------------------------------------------------
|
|
$ git-tag stable-1 1b2e1d63ff
|
|
-------------------------------------------------
|
|
|
|
You can use stable-1 to refer to the commit 1b2e1d63ff.
|
|
|
|
This creates a "lightweight" tag. If the tag is a tag you wish to
|
|
share with others, and possibly sign cryptographically, then you
|
|
should create a tag object instead; see the gitlink:git-tag[1] man
|
|
page for details.
|
|
|
|
Browsing revisions
|
|
------------------
|
|
|
|
The gitlink:git-log[1] command can show lists of commits. On its
|
|
own, it shows all commits reachable from the parent commit; but you
|
|
can also make more specific requests:
|
|
|
|
-------------------------------------------------
|
|
$ git log v2.5.. # commits since (not reachable from) v2.5
|
|
$ git log test..master # commits reachable from master but not test
|
|
$ git log master..test # ...reachable from test but not master
|
|
$ git log master...test # ...reachable from either test or master,
|
|
# but not both
|
|
$ git log --since="2 weeks ago" # commits from the last 2 weeks
|
|
$ git log Makefile # commits which modify Makefile
|
|
$ git log fs/ # ... which modify any file under fs/
|
|
$ git log -S'foo()' # commits which add or remove any file data
|
|
# matching the string 'foo()'
|
|
-------------------------------------------------
|
|
|
|
And of course you can combine all of these; the following finds
|
|
commits since v2.5 which touch the Makefile or any file under fs:
|
|
|
|
-------------------------------------------------
|
|
$ git log v2.5.. Makefile fs/
|
|
-------------------------------------------------
|
|
|
|
You can also ask git log to show patches:
|
|
|
|
-------------------------------------------------
|
|
$ git log -p
|
|
-------------------------------------------------
|
|
|
|
See the "--pretty" option in the gitlink:git-log[1] man page for more
|
|
display options.
|
|
|
|
Note that git log starts with the most recent commit and works
|
|
backwards through the parents; however, since git history can contain
|
|
multiple independant lines of development, the particular order that
|
|
commits are listed in may be somewhat arbitrary.
|
|
|
|
Generating diffs
|
|
----------------
|
|
|
|
You can generate diffs between any two versions using
|
|
gitlink:git-diff[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git diff master..test
|
|
-------------------------------------------------
|
|
|
|
Sometimes what you want instead is a set of patches:
|
|
|
|
-------------------------------------------------
|
|
$ git format-patch master..test
|
|
-------------------------------------------------
|
|
|
|
will generate a file with a patch for each commit reachable from test
|
|
but not from master. Note that if master also has commits which are
|
|
not reachable from test, then the combined result of these patches
|
|
will not be the same as the diff produced by the git-diff example.
|
|
|
|
Viewing old file versions
|
|
-------------------------
|
|
|
|
You can always view an old version of a file by just checking out the
|
|
correct revision first. But sometimes it is more convenient to be
|
|
able to view an old version of a single file without checking
|
|
anything out; this command does that:
|
|
|
|
-------------------------------------------------
|
|
$ git show v2.5:fs/locks.c
|
|
-------------------------------------------------
|
|
|
|
Before the colon may be anything that names a commit, and after it
|
|
may be any path to a file tracked by git.
|
|
|
|
Examples
|
|
--------
|
|
|
|
Check whether two branches point at the same history
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Suppose you want to check whether two branches point at the same point
|
|
in history.
|
|
|
|
-------------------------------------------------
|
|
$ git diff origin..master
|
|
-------------------------------------------------
|
|
|
|
will tell you whether the contents of the project are the same at the
|
|
two branches; in theory, however, it's possible that the same project
|
|
contents could have been arrived at by two different historical
|
|
routes. You could compare the SHA1 id's:
|
|
|
|
-------------------------------------------------
|
|
$ git rev-list origin
|
|
e05db0fd4f31dde7005f075a84f96b360d05984b
|
|
$ git rev-list master
|
|
e05db0fd4f31dde7005f075a84f96b360d05984b
|
|
-------------------------------------------------
|
|
|
|
Or you could recall that the ... operator selects all commits
|
|
contained reachable from either one reference or the other but not
|
|
both: so
|
|
|
|
-------------------------------------------------
|
|
$ git log origin...master
|
|
-------------------------------------------------
|
|
|
|
will return no commits when the two branches are equal.
|
|
|
|
Check which tagged version a given fix was first included in
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Suppose you know that the commit e05db0fd fixed a certain problem.
|
|
You'd like to find the earliest tagged release that contains that
|
|
fix.
|
|
|
|
Of course, there may be more than one answer--if the history branched
|
|
after commit e05db0fd, then there could be multiple "earliest" tagged
|
|
releases.
|
|
|
|
You could just visually inspect the commits since e05db0fd:
|
|
|
|
-------------------------------------------------
|
|
$ gitk e05db0fd..
|
|
-------------------------------------------------
|
|
|
|
...
|
|
|
|
Developing with git
|
|
===================
|
|
|
|
Telling git your name
|
|
---------------------
|
|
|
|
Before creating any commits, you should introduce yourself to git. The
|
|
easiest way to do so is:
|
|
|
|
------------------------------------------------
|
|
$ cat >~/.gitconfig <<\EOF
|
|
[user]
|
|
name = Your Name Comes Here
|
|
email = you@yourdomain.example.com
|
|
EOF
|
|
------------------------------------------------
|
|
|
|
|
|
Creating a new repository
|
|
-------------------------
|
|
|
|
Creating a new repository from scratch is very easy:
|
|
|
|
-------------------------------------------------
|
|
$ mkdir project
|
|
$ cd project
|
|
$ git init
|
|
-------------------------------------------------
|
|
|
|
If you have some initial content (say, a tarball):
|
|
|
|
-------------------------------------------------
|
|
$ tar -xzvf project.tar.gz
|
|
$ cd project
|
|
$ git init
|
|
$ git add . # include everything below ./ in the first commit:
|
|
$ git commit
|
|
-------------------------------------------------
|
|
|
|
[[how-to-make-a-commit]]
|
|
how to make a commit
|
|
--------------------
|
|
|
|
Creating a new commit takes three steps:
|
|
|
|
1. Making some changes to the working directory using your
|
|
favorite editor.
|
|
2. Telling git about your changes.
|
|
3. Creating the commit using the content you told git about
|
|
in step 2.
|
|
|
|
In practice, you can interleave and repeat steps 1 and 2 as many
|
|
times as you want: in order to keep track of what you want committed
|
|
at step 3, git maintains a snapshot of the tree's contents in a
|
|
special staging area called "the index."
|
|
|
|
At the beginning, the content of the index will be identical to
|
|
that of the HEAD. The command "git diff --cached", which shows
|
|
the difference between the HEAD and the index, should therefore
|
|
produce no output at that point.
|
|
|
|
Modifying the index is easy:
|
|
|
|
To update the index with the new contents of a modified file, use
|
|
|
|
-------------------------------------------------
|
|
$ git add path/to/file
|
|
-------------------------------------------------
|
|
|
|
To add the contents of a new file to the index, use
|
|
|
|
-------------------------------------------------
|
|
$ git add path/to/file
|
|
-------------------------------------------------
|
|
|
|
To remove a file from the index and from the working tree,
|
|
|
|
-------------------------------------------------
|
|
$ git rm path/to/file
|
|
-------------------------------------------------
|
|
|
|
After each step you can verify that
|
|
|
|
-------------------------------------------------
|
|
$ git diff --cached
|
|
-------------------------------------------------
|
|
|
|
always shows the difference between the HEAD and the index file--this
|
|
is what you'd commit if you created the commit now--and that
|
|
|
|
-------------------------------------------------
|
|
$ git diff
|
|
-------------------------------------------------
|
|
|
|
shows the difference between the working tree and the index file.
|
|
|
|
Note that "git add" always adds just the current contents of a file
|
|
to the index; further changes to the same file will be ignored unless
|
|
you run git-add on the file again.
|
|
|
|
When you're ready, just run
|
|
|
|
-------------------------------------------------
|
|
$ git commit
|
|
-------------------------------------------------
|
|
|
|
and git will prompt you for a commit message and then create the new
|
|
commmit. Check to make sure it looks like what you expected with
|
|
|
|
-------------------------------------------------
|
|
$ git show
|
|
-------------------------------------------------
|
|
|
|
As a special shortcut,
|
|
|
|
-------------------------------------------------
|
|
$ git commit -a
|
|
-------------------------------------------------
|
|
|
|
will update the index with any files that you've modified or removed
|
|
and create a commit, all in one step.
|
|
|
|
A number of commands are useful for keeping track of what you're
|
|
about to commit:
|
|
|
|
-------------------------------------------------
|
|
$ git diff --cached # difference between HEAD and the index; what
|
|
# would be commited if you ran "commit" now.
|
|
$ git diff # difference between the index file and your
|
|
# working directory; changes that would not
|
|
# be included if you ran "commit" now.
|
|
$ git status # a brief per-file summary of the above.
|
|
-------------------------------------------------
|
|
|
|
creating good commit messages
|
|
-----------------------------
|
|
|
|
Though not required, it's a good idea to begin the commit message
|
|
with a single short (less than 50 character) line summarizing the
|
|
change, followed by a blank line and then a more thorough
|
|
description. Tools that turn commits into email, for example, use
|
|
the first line on the Subject line and the rest of the commit in the
|
|
body.
|
|
|
|
how to merge
|
|
------------
|
|
|
|
You can rejoin two diverging branches of development using
|
|
gitlink:git-merge[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git merge branchname
|
|
-------------------------------------------------
|
|
|
|
merges the development in the branch "branchname" into the current
|
|
branch. If there are conflicts--for example, if the same file is
|
|
modified in two different ways in the remote branch and the local
|
|
branch--then you are warned; the output may look something like this:
|
|
|
|
-------------------------------------------------
|
|
$ git pull . next
|
|
Trying really trivial in-index merge...
|
|
fatal: Merge requires file-level merging
|
|
Nope.
|
|
Merging HEAD with 77976da35a11db4580b80ae27e8d65caf5208086
|
|
Merging:
|
|
15e2162 world
|
|
77976da goodbye
|
|
found 1 common ancestor(s):
|
|
d122ed4 initial
|
|
Auto-merging file.txt
|
|
CONFLICT (content): Merge conflict in file.txt
|
|
Automatic merge failed; fix conflicts and then commit the result.
|
|
-------------------------------------------------
|
|
|
|
Conflict markers are left in the problematic files, and after
|
|
you resolve the conflicts manually, you can update the index
|
|
with the contents and run git commit, as you normally would when
|
|
creating a new file.
|
|
|
|
If you examine the resulting commit using gitk, you will see that it
|
|
has two parents, one pointing to the top of the current branch, and
|
|
one to the top of the other branch.
|
|
|
|
In more detail:
|
|
|
|
[[resolving-a-merge]]
|
|
Resolving a merge
|
|
-----------------
|
|
|
|
When a merge isn't resolved automatically, git leaves the index and
|
|
the working tree in a special state that gives you all the
|
|
information you need to help resolve the merge.
|
|
|
|
Files with conflicts are marked specially in the index, so until you
|
|
resolve the problem and update the index, git commit will fail:
|
|
|
|
-------------------------------------------------
|
|
$ git commit
|
|
file.txt: needs merge
|
|
-------------------------------------------------
|
|
|
|
Also, git status will list those files as "unmerged".
|
|
|
|
All of the changes that git was able to merge automatically are
|
|
already added to the index file, so gitlink:git-diff[1] shows only
|
|
the conflicts. Also, it uses a somewhat unusual syntax:
|
|
|
|
-------------------------------------------------
|
|
$ git diff
|
|
diff --cc file.txt
|
|
index 802992c,2b60207..0000000
|
|
--- a/file.txt
|
|
+++ b/file.txt
|
|
@@@ -1,1 -1,1 +1,5 @@@
|
|
++<<<<<<< HEAD:file.txt
|
|
+Hello world
|
|
++=======
|
|
+ Goodbye
|
|
++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt
|
|
-------------------------------------------------
|
|
|
|
Recall that the commit which will be commited after we resolve this
|
|
conflict will have two parents instead of the usual one: one parent
|
|
will be HEAD, the tip of the current branch; the other will be the
|
|
tip of the other branch, which is stored temporarily in MERGE_HEAD.
|
|
|
|
The diff above shows the differences between the working-tree version
|
|
of file.txt and two previous version: one version from HEAD, and one
|
|
from MERGE_HEAD. So instead of preceding each line by a single "+"
|
|
or "-", it now uses two columns: the first column is used for
|
|
differences between the first parent and the working directory copy,
|
|
and the second for differences between the second parent and the
|
|
working directory copy. Thus after resolving the conflict in the
|
|
obvious way, the diff will look like:
|
|
|
|
-------------------------------------------------
|
|
$ git diff
|
|
diff --cc file.txt
|
|
index 802992c,2b60207..0000000
|
|
--- a/file.txt
|
|
+++ b/file.txt
|
|
@@@ -1,1 -1,1 +1,1 @@@
|
|
- Hello world
|
|
-Goodbye
|
|
++Goodbye world
|
|
-------------------------------------------------
|
|
|
|
This shows that our resolved version deleted "Hello world" from the
|
|
first parent, deleted "Goodbye" from the second parent, and added
|
|
"Goodbye world", which was previously absent from both.
|
|
|
|
The gitlink:git-log[1] command also provides special help for merges:
|
|
|
|
-------------------------------------------------
|
|
$ git log --merge
|
|
-------------------------------------------------
|
|
|
|
This will list all commits which exist only on HEAD or on MERGE_HEAD,
|
|
and which touch an unmerged file.
|
|
|
|
We can now add the resolved version to the index and commit:
|
|
|
|
-------------------------------------------------
|
|
$ git add file.txt
|
|
$ git commit
|
|
-------------------------------------------------
|
|
|
|
Note that the commit message will already be filled in for you with
|
|
some information about the merge. Normally you can just use this
|
|
default message unchanged, but you may add additional commentary of
|
|
your own if desired.
|
|
|
|
[[undoing-a-merge]]
|
|
undoing a merge
|
|
---------------
|
|
|
|
If you get stuck and decide to just give up and throw the whole mess
|
|
away, you can always return to the pre-merge state with
|
|
|
|
-------------------------------------------------
|
|
$ git reset --hard HEAD
|
|
-------------------------------------------------
|
|
|
|
Or, if you've already commited the merge that you want to throw away,
|
|
|
|
-------------------------------------------------
|
|
$ git reset --hard HEAD^
|
|
-------------------------------------------------
|
|
|
|
However, this last command can be dangerous in some cases--never
|
|
throw away a commit you have already committed if that commit may
|
|
itself have been merged into another branch, as doing so may confuse
|
|
further merges.
|
|
|
|
Fast-forward merges
|
|
-------------------
|
|
|
|
There is one special case not mentioned above, which is treated
|
|
differently. Normally, a merge results in a merge commit, with two
|
|
parents, one pointing at each of the two lines of development that
|
|
were merged.
|
|
|
|
However, if one of the two lines of development is completely
|
|
contained within the other--so every commit present in the one is
|
|
already contained in the other--then git just performs a
|
|
<<fast-forwards,fast forward>>; the head of the current branch is
|
|
moved forward to point at the head of the merged-in branch, without
|
|
any new commits being created.
|
|
|
|
Fixing mistakes
|
|
---------------
|
|
|
|
If you've messed up the working tree, but haven't yet committed your
|
|
mistake, you can return the entire working tree to the last committed
|
|
state with
|
|
|
|
-------------------------------------------------
|
|
$ git reset --hard HEAD
|
|
-------------------------------------------------
|
|
|
|
If you make a commit that you later wish you hadn't, there are two
|
|
fundamentally different ways to fix the problem:
|
|
|
|
1. You can create a new commit that undoes whatever was done
|
|
by the previous commit. This is the correct thing if your
|
|
mistake has already been made public.
|
|
|
|
2. You can go back and modify the old commit. You should
|
|
never do this if you have already made the history public;
|
|
git does not normally expect the "history" of a project to
|
|
change, and cannot correctly perform repeated merges from
|
|
a branch that has had its history changed.
|
|
|
|
Fixing a mistake with a new commit
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Creating a new commit that reverts an earlier change is very easy;
|
|
just pass the gitlink:git-revert[1] command a reference to the bad
|
|
commit; for example, to revert the most recent commit:
|
|
|
|
-------------------------------------------------
|
|
$ git revert HEAD
|
|
-------------------------------------------------
|
|
|
|
This will create a new commit which undoes the change in HEAD. You
|
|
will be given a chance to edit the commit message for the new commit.
|
|
|
|
You can also revert an earlier change, for example, the next-to-last:
|
|
|
|
-------------------------------------------------
|
|
$ git revert HEAD^
|
|
-------------------------------------------------
|
|
|
|
In this case git will attempt to undo the old change while leaving
|
|
intact any changes made since then. If more recent changes overlap
|
|
with the changes to be reverted, then you will be asked to fix
|
|
conflicts manually, just as in the case of <<resolving-a-merge,
|
|
resolving a merge>>.
|
|
|
|
Fixing a mistake by editing history
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
If the problematic commit is the most recent commit, and you have not
|
|
yet made that commit public, then you may just
|
|
<<undoing-a-merge,destroy it using git-reset>>.
|
|
|
|
Alternatively, you
|
|
can edit the working directory and update the index to fix your
|
|
mistake, just as if you were going to <<how-to-make-a-commit,create a
|
|
new commit>>, then run
|
|
|
|
-------------------------------------------------
|
|
$ git commit --amend
|
|
-------------------------------------------------
|
|
|
|
which will replace the old commit by a new commit incorporating your
|
|
changes, giving you a chance to edit the old commit message first.
|
|
|
|
Again, you should never do this to a commit that may already have
|
|
been merged into another branch; use gitlink:git-revert[1] instead in
|
|
that case.
|
|
|
|
It is also possible to edit commits further back in the history, but
|
|
this is an advanced topic to be left for
|
|
<<cleaning-up-history,another chapter>>.
|
|
|
|
Checking out an old version of a file
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
In the process of undoing a previous bad change, you may find it
|
|
useful to check out an older version of a particular file using
|
|
gitlink:git-checkout[1]. We've used git checkout before to switch
|
|
branches, but it has quite different behavior if it is given a path
|
|
name: the command
|
|
|
|
-------------------------------------------------
|
|
$ git checkout HEAD^ path/to/file
|
|
-------------------------------------------------
|
|
|
|
replaces path/to/file by the contents it had in the commit HEAD^, and
|
|
also updates the index to match. It does not change branches.
|
|
|
|
If you just want to look at an old version of the file, without
|
|
modifying the working directory, you can do that with
|
|
gitlink:git-show[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git show HEAD^ path/to/file
|
|
-------------------------------------------------
|
|
|
|
which will display the given version of the file.
|
|
|
|
Ensuring good performance
|
|
-------------------------
|
|
|
|
On large repositories, git depends on compression to keep the history
|
|
information from taking up to much space on disk or in memory.
|
|
|
|
This compression is not performed automatically. Therefore you
|
|
should occasionally run
|
|
|
|
-------------------------------------------------
|
|
$ git gc
|
|
-------------------------------------------------
|
|
|
|
to recompress the archive and to prune any commits which are no
|
|
longer referred to anywhere. This can be very time-consuming, and
|
|
you should not modify the repository while it is working, so you
|
|
should run it while you are not working.
|
|
|
|
Sharing development with others
|
|
===============================
|
|
|
|
[[getting-updates-with-git-pull]]
|
|
Getting updates with git pull
|
|
-----------------------------
|
|
|
|
After you clone a repository and make a few changes of your own, you
|
|
may wish to check the original repository for updates and merge them
|
|
into your own work.
|
|
|
|
We have already seen <<Updating-a-repository-with-git-fetch,how to
|
|
keep remote tracking branches up to date>> with gitlink:git-fetch[1],
|
|
and how to merge two branches. So you can merge in changes from the
|
|
original repository's master branch with:
|
|
|
|
-------------------------------------------------
|
|
$ git fetch
|
|
$ git merge origin/master
|
|
-------------------------------------------------
|
|
|
|
However, the gitlink:git-pull[1] command provides a way to do this in
|
|
one step:
|
|
|
|
-------------------------------------------------
|
|
$ git pull origin master
|
|
-------------------------------------------------
|
|
|
|
In fact, "origin" is normally the default repository to pull from,
|
|
and the default branch is normally the HEAD of the remote repository,
|
|
so often you can accomplish the above with just
|
|
|
|
-------------------------------------------------
|
|
$ git pull
|
|
-------------------------------------------------
|
|
|
|
See the descriptions of the branch.<name>.remote and
|
|
branch.<name>.merge options in gitlink:git-repo-config[1] to learn
|
|
how to control these defaults depending on the current branch.
|
|
|
|
In addition to saving you keystrokes, "git pull" also helps you by
|
|
producing a default commit message documenting the branch and
|
|
repository that you pulled from.
|
|
|
|
(But note that no such commit will be created in the case of a
|
|
<<fast-forwards,fast forward>>; instead, your branch will just be
|
|
updated to point to the latest commit from the upstream branch).
|
|
|
|
The git-pull command can also be given "." as the "remote" repository, in
|
|
which case it just merges in a branch from the current repository; so
|
|
the commands
|
|
|
|
-------------------------------------------------
|
|
$ git pull . branch
|
|
$ git merge branch
|
|
-------------------------------------------------
|
|
|
|
are roughly equivalent. The former is actually very commonly used.
|
|
|
|
Submitting patches to a project
|
|
-------------------------------
|
|
|
|
If you just have a few changes, the simplest way to submit them may
|
|
just be to send them as patches in email:
|
|
|
|
First, use gitlink:git-format-patches[1]; for example:
|
|
|
|
-------------------------------------------------
|
|
$ git format-patch origin
|
|
-------------------------------------------------
|
|
|
|
will produce a numbered series of files in the current directory, one
|
|
for each patch in the current branch but not in origin/HEAD.
|
|
|
|
You can then import these into your mail client and send them by
|
|
hand. However, if you have a lot to send at once, you may prefer to
|
|
use the gitlink:git-send-email[1] script to automate the process.
|
|
Consult the mailing list for your project first to determine how they
|
|
prefer such patches be handled.
|
|
|
|
Importing patches to a project
|
|
------------------------------
|
|
|
|
Git also provides a tool called gitlink:git-am[1] (am stands for
|
|
"apply mailbox"), for importing such an emailed series of patches.
|
|
Just save all of the patch-containing messages, in order, into a
|
|
single mailbox file, say "patches.mbox", then run
|
|
|
|
-------------------------------------------------
|
|
$ git am -3 patches.mbox
|
|
-------------------------------------------------
|
|
|
|
Git will apply each patch in order; if any conflicts are found, it
|
|
will stop, and you can fix the conflicts as described in
|
|
"<<resolving-a-merge,Resolving a merge>>". (The "-3" option tells
|
|
git to perform a merge; if you would prefer it just to abort and
|
|
leave your tree and index untouched, you may omit that option.)
|
|
|
|
Once the index is updated with the results of the conflict
|
|
resolution, instead of creating a new commit, just run
|
|
|
|
-------------------------------------------------
|
|
$ git am --resolved
|
|
-------------------------------------------------
|
|
|
|
and git will create the commit for you and continue applying the
|
|
remaining patches from the mailbox.
|
|
|
|
The final result will be a series of commits, one for each patch in
|
|
the original mailbox, with authorship and commit log message each
|
|
taken from the message containing each patch.
|
|
|
|
[[setting-up-a-public-repository]]
|
|
Setting up a public repository
|
|
------------------------------
|
|
|
|
Another way to submit changes to a project is to simply tell the
|
|
maintainer of that project to pull from your repository, exactly as
|
|
you did in the section "<<getting-updates-with-git-pull, Getting
|
|
updates with git pull>>".
|
|
|
|
If you and maintainer both have accounts on the same machine, then
|
|
then you can just pull changes from each other's repositories
|
|
directly; note that all of the command (gitlink:git-clone[1],
|
|
git-fetch[1], git-pull[1], etc.) which accept a URL as an argument
|
|
will also accept a local file patch; so, for example, you can
|
|
use
|
|
|
|
-------------------------------------------------
|
|
$ git clone /path/to/repository
|
|
$ git pull /path/to/other/repository
|
|
-------------------------------------------------
|
|
|
|
If this sort of setup is inconvenient or impossible, another (more
|
|
common) option is to set up a public repository on a public server.
|
|
This also allows you to cleanly separate private work in progress
|
|
from publicly visible work.
|
|
|
|
You will continue to do your day-to-day work in your personal
|
|
repository, but periodically "push" changes from your personal
|
|
repository into your public repository, allowing other developers to
|
|
pull from that repository. So the flow of changes, in a situation
|
|
where there is one other developer with a public repository, looks
|
|
like this:
|
|
|
|
you push
|
|
your personal repo ------------------> your public repo
|
|
^ |
|
|
| |
|
|
| you pull | they pull
|
|
| |
|
|
| |
|
|
| they push V
|
|
their public repo <------------------- their repo
|
|
|
|
Now, assume your personal repository is in the directory ~/proj. We
|
|
first create a new clone of the repository:
|
|
|
|
-------------------------------------------------
|
|
$ git clone --bare proj-clone.git
|
|
-------------------------------------------------
|
|
|
|
The resulting directory proj-clone.git will contains a "bare" git
|
|
repository--it is just the contents of the ".git" directory, without
|
|
a checked-out copy of a working directory.
|
|
|
|
Next, copy proj-clone.git to the server where you plan to host the
|
|
public repository. You can use scp, rsync, or whatever is most
|
|
convenient.
|
|
|
|
If somebody else maintains the public server, they may already have
|
|
set up a git service for you, and you may skip to the section
|
|
"<<pushing-changes-to-a-public-repository,Pushing changes to a public
|
|
repository>>", below.
|
|
|
|
Otherwise, the following sections explain how to export your newly
|
|
created public repository:
|
|
|
|
[[exporting-via-http]]
|
|
Exporting a git repository via http
|
|
-----------------------------------
|
|
|
|
The git protocol gives better performance and reliability, but on a
|
|
host with a web server set up, http exports may be simpler to set up.
|
|
|
|
All you need to do is place the newly created bare git repository in
|
|
a directory that is exported by the web server, and make some
|
|
adjustments to give web clients some extra information they need:
|
|
|
|
-------------------------------------------------
|
|
$ mv proj.git /home/you/public_html/proj.git
|
|
$ cd proj.git
|
|
$ git update-server-info
|
|
$ chmod a+x hooks/post-update
|
|
-------------------------------------------------
|
|
|
|
(For an explanation of the last two lines, see
|
|
gitlink:git-update-server-info[1], and the documentation
|
|
link:hooks.txt[Hooks used by git].)
|
|
|
|
Advertise the url of proj.git. Anybody else should then be able to
|
|
clone or pull from that url, for example with a commandline like:
|
|
|
|
-------------------------------------------------
|
|
$ git clone http://yourserver.com/~you/proj.git
|
|
-------------------------------------------------
|
|
|
|
(See also
|
|
link:howto/setup-git-server-over-http.txt[setup-git-server-over-http]
|
|
for a slightly more sophisticated setup using WebDAV which also
|
|
allows pushing over http.)
|
|
|
|
[[exporting-via-git]]
|
|
Exporting a git repository via the git protocol
|
|
-----------------------------------------------
|
|
|
|
This is the preferred method.
|
|
|
|
For now, we refer you to the gitlink:git-daemon[1] man page for
|
|
instructions. (See especially the examples section.)
|
|
|
|
[[pushing-changes-to-a-public-repository]]
|
|
Pushing changes to a public repository
|
|
--------------------------------------
|
|
|
|
Note that the two techniques outline above (exporting via
|
|
<<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other
|
|
maintainers to fetch your latest changes, but they do not allow write
|
|
access, which you will need to update the public repository with the
|
|
latest changes created in your private repository.
|
|
|
|
The simplest way to do this is using gitlink:git-push[1] and ssh; to
|
|
update the remote branch named "master" with the latest state of your
|
|
branch named "master", run
|
|
|
|
-------------------------------------------------
|
|
$ git push ssh://yourserver.com/~you/proj.git master:master
|
|
-------------------------------------------------
|
|
|
|
or just
|
|
|
|
-------------------------------------------------
|
|
$ git push ssh://yourserver.com/~you/proj.git master
|
|
-------------------------------------------------
|
|
|
|
As with git-fetch, git-push will complain if this does not result in
|
|
a <<fast-forwards,fast forward>>. Normally this is a sign of
|
|
something wrong. However, if you are sure you know what you're
|
|
doing, you may force git-push to perform the update anyway by
|
|
proceeding the branch name by a plus sign:
|
|
|
|
-------------------------------------------------
|
|
$ git push ssh://yourserver.com/~you/proj.git +master
|
|
-------------------------------------------------
|
|
|
|
As with git-fetch, you may also set up configuration options to
|
|
save typing; so, for example, after
|
|
|
|
-------------------------------------------------
|
|
$ cat >.git/config <<EOF
|
|
[remote "public-repo"]
|
|
url = ssh://yourserver.com/~you/proj.git
|
|
EOF
|
|
-------------------------------------------------
|
|
|
|
you should be able to perform the above push with just
|
|
|
|
-------------------------------------------------
|
|
$ git push public-repo master
|
|
-------------------------------------------------
|
|
|
|
See the explanations of the remote.<name>.url, branch.<name>.remote,
|
|
and remote.<name>.push options in gitlink:git-repo-config[1] for
|
|
details.
|
|
|
|
Setting up a shared repository
|
|
------------------------------
|
|
|
|
Another way to collaborate is by using a model similar to that
|
|
commonly used in CVS, where several developers with special rights
|
|
all push to and pull from a single shared repository. See
|
|
link:cvs-migration.txt[git for CVS users] for instructions on how to
|
|
set this up.
|
|
|
|
Allow web browsing of a repository
|
|
----------------------------------
|
|
|
|
TODO: Brief setup-instructions for gitweb
|
|
|
|
Examples
|
|
--------
|
|
|
|
TODO: topic branches, typical roles as in everyday.txt, ?
|
|
|
|
|
|
Working with other version control systems
|
|
==========================================
|
|
|
|
TODO: CVS, Subversion, series-of-release-tarballs, ?
|
|
|
|
[[cleaning-up-history]]
|
|
Rewriting history and maintaining patch series
|
|
==============================================
|
|
|
|
Normally commits are only added to a project, never taken away or
|
|
replaced. Git is designed with this assumption, and violating it will
|
|
cause git's merge machinery (for example) to do the wrong thing.
|
|
|
|
However, there is a situation in which it can be useful to violate this
|
|
assumption.
|
|
|
|
Creating the perfect patch series
|
|
---------------------------------
|
|
|
|
Suppose you are a contributor to a large project, and you want to add a
|
|
complicated feature, and to present it to the other developers in a way
|
|
that makes it easy for them to read your changes, verify that they are
|
|
correct, and understand why you made each change.
|
|
|
|
If you present all of your changes as a single patch (or commit), they may
|
|
find it is too much to digest all at once.
|
|
|
|
If you present them with the entire history of your work, complete with
|
|
mistakes, corrections, and dead ends, they may be overwhelmed.
|
|
|
|
So the ideal is usually to produce a series of patches such that:
|
|
|
|
1. Each patch can be applied in order.
|
|
|
|
2. Each patch includes a single logical change, together with a
|
|
message explaining the change.
|
|
|
|
3. No patch introduces a regression: after applying any initial
|
|
part of the series, the resulting project still compiles and
|
|
works, and has no bugs that it didn't have before.
|
|
|
|
4. The complete series produces the same end result as your own
|
|
(probably much messier!) development process did.
|
|
|
|
We will introduce some tools that can help you do this, explain how to use
|
|
them, and then explain some of the problems that can arise because you are
|
|
rewriting history.
|
|
|
|
Keeping a patch series up to date using git-rebase
|
|
--------------------------------------------------
|
|
|
|
Suppose you have a series of commits in a branch "mywork", which
|
|
originally branched off from "origin".
|
|
|
|
Suppose you create a branch "mywork" on a remote-tracking branch "origin",
|
|
and created some commits on top of it:
|
|
|
|
-------------------------------------------------
|
|
$ git checkout -b mywork origin
|
|
$ vi file.txt
|
|
$ git commit
|
|
$ vi otherfile.txt
|
|
$ git commit
|
|
...
|
|
-------------------------------------------------
|
|
|
|
You have performed no merges into mywork, so it is just a simple linear
|
|
sequence of patches on top of "origin":
|
|
|
|
|
|
o--o--o <-- origin
|
|
\
|
|
o--o--o <-- mywork
|
|
|
|
Some more interesting work has been done in the upstream project, and
|
|
"origin" has advanced:
|
|
|
|
o--o--O--o--o--o <-- origin
|
|
\
|
|
a--b--c <-- mywork
|
|
|
|
At this point, you could use "pull" to merge your changes back in;
|
|
the result would create a new merge commit, like this:
|
|
|
|
|
|
o--o--O--o--o--o <-- origin
|
|
\ \
|
|
a--b--c--m <-- mywork
|
|
|
|
However, if you prefer to keep the history in mywork a simple series of
|
|
commits without any merges, you may instead choose to use
|
|
gitlink:git-rebase[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git checkout mywork
|
|
$ git rebase origin
|
|
-------------------------------------------------
|
|
|
|
This will remove each of your commits from mywork, temporarily saving them
|
|
as patches (in a directory named ".dotest"), update mywork to point at the
|
|
latest version of origin, then apply each of the saved patches to the new
|
|
mywork. The result will look like:
|
|
|
|
|
|
o--o--O--o--o--o <-- origin
|
|
\
|
|
a'--b'--c' <-- mywork
|
|
|
|
In the process, it may discover conflicts. In that case it will stop and
|
|
allow you to fix the conflicts as described in
|
|
"<<resolving-a-merge,Resolving a merge>>".
|
|
|
|
XXX: no, maybe not: git diff doesn't produce very useful results, and there's
|
|
no MERGE_HEAD.
|
|
|
|
Once the index is updated with
|
|
the results of the conflict resolution, instead of creating a new commit,
|
|
just run
|
|
|
|
-------------------------------------------------
|
|
$ git rebase --continue
|
|
-------------------------------------------------
|
|
|
|
and git will continue applying the rest of the patches.
|
|
|
|
At any point you may use the --abort option to abort this process and
|
|
return mywork to the state it had before you started the rebase:
|
|
|
|
-------------------------------------------------
|
|
$ git rebase --abort
|
|
-------------------------------------------------
|
|
|
|
Reordering or selecting from a patch series
|
|
-------------------------------------------
|
|
|
|
Given one existing commit, the gitlink:git-cherry-pick[1] command allows
|
|
you to apply the change introduced by that commit and create a new commit
|
|
that records it.
|
|
|
|
This can be useful for modifying a patch series.
|
|
|
|
TODO: elaborate
|
|
|
|
Other tools
|
|
-----------
|
|
|
|
There are numerous other tools, such as stgit, which exist for the purpose
|
|
of maintianing a patch series. These are out of the scope of this manual.
|
|
|
|
Problems with rewriting history
|
|
-------------------------------
|
|
|
|
The primary problem with rewriting the history of a branch has to do with
|
|
merging.
|
|
|
|
TODO: elaborate
|
|
|
|
|
|
Git internals
|
|
=============
|
|
|
|
Architectural overview
|
|
----------------------
|
|
|
|
TODO: Sources, README, core-tutorial, tutorial-2.txt, technical/
|
|
|
|
Glossary of git terms
|
|
=====================
|
|
|
|
include::glossary.txt[]
|
|
|
|
Notes and todo list for this manual
|
|
===================================
|
|
|
|
This is a work in progress.
|
|
|
|
The basic requirements:
|
|
- It must be readable in order, from beginning to end, by
|
|
someone intelligent with a basic grasp of the unix
|
|
commandline, but without any special knowledge of git. If
|
|
necessary, any other prerequisites should be specifically
|
|
mentioned as they arise.
|
|
- Whenever possible, section headings should clearly describe
|
|
the task they explain how to do, in language that requires
|
|
no more knowledge than necessary: for example, "importing
|
|
patches into a project" rather than "the git-am command"
|
|
|
|
Think about how to create a clear chapter dependency graph that will
|
|
allow people to get to important topics without necessarily reading
|
|
everything in between.
|
|
|
|
Scan Documentation/ for other stuff left out; in particular:
|
|
howto's
|
|
README
|
|
some of technical/?
|
|
hooks
|
|
etc.
|
|
|
|
Scan email archives for other stuff left out
|
|
|
|
Scan man pages to see if any assume more background than this manual
|
|
provides.
|
|
|
|
Simplify beginning by suggesting disconnected head instead of
|
|
temporary branch creation.
|
|
|
|
Explain how to refer to file stages in the "how to resolve a merge"
|
|
section: diff -1, -2, -3, --ours, --theirs :1:/path notation. The
|
|
"git ls-files --unmerged --stage" thing is sorta useful too,
|
|
actually. And note gitk --merge. Also what's easiest way to see
|
|
common merge base? Note also text where I claim rebase and am
|
|
conflicts are resolved like merges isn't generally true, at least by
|
|
default--fix.
|
|
|
|
Add more good examples. Entire sections of just cookbook examples
|
|
might be a good idea; maybe make an "advanced examples" section a
|
|
standard end-of-chapter section?
|
|
|
|
Include cross-references to the glossary, where appropriate.
|
|
|
|
Add quickstart as first chapter.
|
|
|
|
To document:
|
|
reflogs, git reflog expire
|
|
shallow clones?? See draft 1.5.0 release notes for some documentation.
|