cvs-migration documentation update
Here's some changes to the cvs-migration.txt. As usual, in my attempt to make things clearer someone may have found I've made them less so, or I may have just gotten something wrong; so any review is welcomed. I can break up this sort of thing into smaller steps if preferred, the monolothic patch is just a bit simpler for me for this sort of thing. I moved the material describing shared repository management from core-tutorial.txt to cvs-migration.txt, where it seems more appropriate, and combined two sections to eliminate some redundancy. I also revised the earlier sections of cvs-migration.txt, mainly trying to make it more concise. I've left the last section of cvs-migration.txt (on CVS annotate alternatives) alone for now. Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu> Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
J. Bruce Fields
Junio C Hamano
parent
1506fc34f7
commit
b8bc67cef3
@ -1623,123 +1623,7 @@ suggested in the previous section may be new to you. You do not
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have to worry. git supports "shared public repository" style of
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cooperation you are probably more familiar with as well.
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For this, set up a public repository on a machine that is
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reachable via SSH by people with "commit privileges". Put the
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committers in the same user group and make the repository
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writable by that group. Make sure their umasks are set up to
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allow group members to write into directories other members
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have created.
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You, as an individual committer, then:
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- First clone the shared repository to a local repository:
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------------------------------------------------
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$ git clone repo.shared.xz:/pub/scm/project.git/ my-project
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$ cd my-project
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$ hack away
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------------------------------------------------
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- Merge the work others might have done while you were hacking
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away:
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------------------------------------------------
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$ git pull origin
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$ test the merge result
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------------------------------------------------
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[NOTE]
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================================
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The first `git clone` would have placed the following in
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`my-project/.git/remotes/origin` file, and that's why this and
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the next step work.
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------------
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URL: repo.shared.xz:/pub/scm/project.git/ my-project
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Pull: master:origin
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------------
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================================
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- push your work as the new head of the shared
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repository.
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------------------------------------------------
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$ git push origin master
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------------------------------------------------
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If somebody else pushed into the same shared repository while
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you were working locally, `git push` in the last step would
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complain, telling you that the remote `master` head does not
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fast forward. You need to pull and merge those other changes
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back before you push your work when it happens.
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The `git push` command without any explicit refspec parameter
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pushes the refs that exist both in the local repository and the
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remote repository. So the last `push` can be done with either
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one of these:
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------------
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$ git push origin
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$ git push repo.shared.xz:/pub/scm/project.git/
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------------
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as long as the shared repository does not have any branches
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other than `master`.
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[NOTE]
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============
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If you created your shared repository by cloning from somewhere
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else, you may have the `origin` branch. Your developers
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typically do not use that branch; remove it. Otherwise, that
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would be pushed back by the `git push origin` because your
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developers' repository would surely have `origin` branch to keep
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track of the shared repository, and would be counted as "exist
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on both ends".
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============
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Advanced Shared Repository Management
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-------------------------------------
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Being able to push into a shared repository means being able to
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write into it. If your developers are coming over the network,
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this means you, as the repository administrator, need to give
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each of them an SSH access to the shared repository machine.
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In some cases, though, you may not want to give a normal shell
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account to them, but want to restrict them to be able to only
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do `git push` into the repository and nothing else.
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You can achieve this by setting the login shell of your
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developers on the shared repository host to `git-shell` program.
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[NOTE]
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Most likely you would also need to list `git-shell` program in
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`/etc/shells` file.
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This restricts the set of commands that can be run from incoming
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SSH connection for these users to only `receive-pack` and
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`upload-pack`, so the only thing they can do are `git fetch` and
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`git push`.
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You still need to create UNIX user accounts for each developer,
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and put them in the same group. Make sure that the repository
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shared among these developers is writable by that group.
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. Initializing the shared repository with `git-init-db --shared`
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helps somewhat.
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. Run the following in the shared repository:
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+
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------------
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$ chgrp -R $group repo.git
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$ find repo.git -type d -print | xargs chmod ug+rwx,g+s
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$ GIT_DIR=repo.git git repo-config core.sharedrepository true
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------------
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The above measures make sure that directories lazily created in
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`$GIT_DIR` are writable by group members. You, as the
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repository administrator, are still responsible to make sure
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your developers belong to that shared repository group and set
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their umask to a value no stricter than 027 (i.e. at least allow
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reading and searching by group members).
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You can implement finer grained branch policies using update
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hooks. There is a document ("control access to branches") in
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Documentation/howto by Carl Baldwin and JC outlining how to (1)
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limit access to branch per user, (2) forbid overwriting existing
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tags.
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See link:cvs-migration.txt[git for CVS users] for the details.
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Bundling your work together
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---------------------------
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@ -1,126 +1,182 @@
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git for CVS users
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=================
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Ok, so you're a CVS user. That's ok, it's a treatable condition, and the
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first step to recovery is admitting you have a problem. The fact that
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you are reading this file means that you may be well on that path
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already.
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So you're a CVS user. That's ok, it's a treatable condition. The job of
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this document is to put you on the road to recovery, by helping you
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convert an existing cvs repository to git, and by showing you how to use a
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git repository in a cvs-like fashion.
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The thing about CVS is that it absolutely sucks as a source control
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manager, and you'll thus be happy with almost anything else. git,
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however, may be a bit 'too' different (read: "good") for your taste, and
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does a lot of things differently.
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Some basic familiarity with git is required. This
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link:tutorial.html[tutorial introduction to git] should be sufficient.
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One particular suckage of CVS is very hard to work around: CVS is
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basically a tool for tracking 'file' history, while git is a tool for
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tracking 'project' history. This sometimes causes problems if you are
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used to doing very strange things in CVS, in particular if you're doing
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things like making branches of just a subset of the project. git can't
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track that, since git never tracks things on the level of an individual
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file, only on the whole project level.
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First, note some ways that git differs from CVS:
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The good news is that most people don't do that, and in fact most sane
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people think it's a bug in CVS that makes it tag (and check in changes)
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one file at a time. So most projects you'll ever see will use CVS
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'as if' it was sane. In which case you'll find it very easy indeed to
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move over to git.
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* Commits are atomic and project-wide, not per-file as in CVS.
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First off: this is not a git tutorial. See
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link:tutorial.html[Documentation/tutorial.txt] for how git
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actually works. This is more of a random collection of gotcha's
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and notes on converting from CVS to git.
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* Offline work is supported: you can make multiple commits locally,
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then submit them when you're ready.
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Second: CVS has the notion of a "repository" as opposed to the thing
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that you're actually working in (your working directory, or your
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"checked out tree"). git does not have that notion at all, and all git
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working directories 'are' the repositories. However, you can easily
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emulate the CVS model by having one special "global repository", which
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people can synchronize with. See details later, but in the meantime
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just keep in mind that with git, every checked out working tree will
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have a full revision control history of its own.
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* Branching is fast and easy.
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* Every working tree contains a repository with a full copy of the
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project history, and no repository is inherently more important than
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any other. However, you can emulate the CVS model by designating a
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single shared repository which people can synchronize with; see below
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for details.
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Importing a CVS archive
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-----------------------
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Ok, you have an old project, and you want to at least give git a chance
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to see how it performs. The first thing you want to do (after you've
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gone through the git tutorial, and generally familiarized yourself with
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how to commit stuff etc in git) is to create a git'ified version of your
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CVS archive.
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First, install version 2.1 or higher of cvsps from
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link:http://www.cobite.com/cvsps/[http://www.cobite.com/cvsps/] and make
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sure it is in your path. The magic command line is then
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Happily, that's very easy indeed. git will do it for you, although git
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will need the help of a program called "cvsps":
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-------------------------------------------
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$ git cvsimport -v -d <cvsroot> -C <destination> <module>
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-------------------------------------------
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http://www.cobite.com/cvsps/
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This puts a git archive of the named CVS module in the directory
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<destination>, which will be created if necessary. The -v option makes
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the conversion script very chatty.
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which is not actually related to git at all, but which makes CVS usage
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look almost sane (ie you almost certainly want to have it even if you
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decide to stay with CVS). However, git will want 'at least' version 2.1
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of cvsps (available at the address above), and in fact will currently
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refuse to work with anything else.
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The import checks out from CVS every revision of every file. Reportedly
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cvsimport can average some twenty revisions per second, so for a
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medium-sized project this should not take more than a couple of minutes.
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Larger projects or remote repositories may take longer.
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Once you've gotten (and installed) cvsps, you may or may not want to get
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any more familiar with it, but make sure it is in your path. After that,
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the magic command line is
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The main trunk is stored in the git branch named `origin`, and additional
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CVS branches are stored in git branches with the same names. The most
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recent version of the main trunk is also left checked out on the `master`
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branch, so you can start adding your own changes right away.
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git cvsimport -v -d <cvsroot> -C <destination> <module>
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The import is incremental, so if you call it again next month it will
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fetch any CVS updates that have been made in the meantime. For this to
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work, you must not modify the imported branches; instead, create new
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branches for your own changes, and merge in the imported branches as
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necessary.
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which will do exactly what you'd think it does: it will create a git
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archive of the named CVS module. The new archive will be created in the
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subdirectory named <destination>; it'll be created if it doesn't exist.
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Default is the local directory.
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Development Models
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------------------
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It can take some time to actually do the conversion for a large archive
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since it involves checking out from CVS every revision of every file,
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and the conversion script is reasonably chatty unless you omit the '-v'
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option, but on some not very scientific tests it averaged about twenty
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revisions per second, so a medium-sized project should not take more
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than a couple of minutes. For larger projects or remote repositories,
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the process may take longer.
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CVS users are accustomed to giving a group of developers commit access to
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a common repository. In the next section we'll explain how to do this
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with git. However, the distributed nature of git allows other development
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models, and you may want to first consider whether one of them might be a
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better fit for your project.
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After the (initial) import is done, the CVS archive's current head
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revision will be checked out -- thus, you can start adding your own
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changes right away.
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For example, you can choose a single person to maintain the project's
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primary public repository. Other developers then clone this repository
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and each work in their own clone. When they have a series of changes that
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they're happy with, they ask the maintainer to pull from the branch
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containing the changes. The maintainer reviews their changes and pulls
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them into the primary repository, which other developers pull from as
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necessary to stay coordinated. The Linux kernel and other projects use
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variants of this model.
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The import is incremental, i.e. if you call it again next month it'll
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fetch any CVS updates that have been happening in the meantime. The
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cut-off is date-based, so don't change the branches that were imported
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from CVS.
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With a small group, developers may just pull changes from each other's
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repositories without the need for a central maintainer.
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You can merge those updates (or, in fact, a different CVS branch) into
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your main branch:
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Emulating the CVS Development Model
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-----------------------------------
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git resolve HEAD origin "merge with current CVS HEAD"
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Start with an ordinary git working directory containing the project, and
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remove the checked-out files, keeping just the bare .git directory:
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The HEAD revision from CVS is named "origin", not "HEAD", because git
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already uses "HEAD". (If you don't like 'origin', use cvsimport's
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'-o' option to change it.)
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------------------------------------------------
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$ mv project/.git /pub/repo.git
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$ rm -r project/
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------------------------------------------------
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Next, give every team member read/write access to this repository. One
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easy way to do this is to give all the team members ssh access to the
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machine where the repository is hosted. If you don't want to give them a
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full shell on the machine, there is a restricted shell which only allows
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users to do git pushes and pulls; see gitlink:git-shell[1].
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Emulating CVS behaviour
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-----------------------
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Put all the committers should in the same group, and make the repository
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writable by that group:
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------------------------------------------------
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$ chgrp -R $group repo.git
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$ find repo.git -mindepth 1 -type d |xargs chmod ug+rwx,g+s
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$ GIT_DIR=repo.git git repo-config core.sharedrepository true
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------------------------------------------------
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So, by now you are convinced you absolutely want to work with git, but
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at the same time you absolutely have to have a central repository.
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Step back and think again. Okay, you still need a single central
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repository? There are several ways to go about that:
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Make sure committers have a umask of at most 027, so that the directories
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they create are writable and searchable by other group members.
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1. Designate a person responsible to pull all branches. Make the
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repository of this person public, and make every team member
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pull regularly from it.
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Suppose this repository is now set up in /pub/repo.git on the host
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foo.com. Then as an individual commiter you can clone the shared
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repository:
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2. Set up a public repository with read/write access for every team
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member. Use "git pull/push" as you used "cvs update/commit". Be
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sure that your repository is up to date before pushing, just
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like you used to do with "cvs commit"; your push will fail if
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what you are pushing is not up to date.
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------------------------------------------------
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$ git clone foo.com:/pub/repo.git/ my-project
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$ cd my-project
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------------------------------------------------
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3. Make the repository of every team member public. It is the
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responsibility of each single member to pull from every other
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team member.
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and hack away. The equivalent of `cvs update` is
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------------------------------------------------
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$ git pull origin
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------------------------------------------------
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which merges in any work that others might have done since the clone
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operation.
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[NOTE]
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================================
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The first `git clone` places the following in the
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`my-project/.git/remotes/origin` file, and that's why the previous step
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and the next step both work.
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------------
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URL: foo.com:/pub/project.git/ my-project
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Pull: master:origin
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------------
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================================
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You can update the shared repository with your changes using:
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------------------------------------------------
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$ git push origin master
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------------------------------------------------
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If some else has updated the repository more recently, `git push`, like
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`cvs commit`, will complain, in which case you must pull any changes
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before attempting the push again.
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In the `git push` command above we specify the name of the remote branch
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to update (`master`). If we leave that out, `git push` tries to update
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any branches in the remote repository that have the same name as a branch
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in the local repository. So the last `push` can be done with either of:
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------------
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$ git push origin
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$ git push repo.shared.xz:/pub/scm/project.git/
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------------
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as long as the shared repository does not have any branches
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other than `master`.
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[NOTE]
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============
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Because of this behaviour, if the shared repository and the developer's
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repository both have branches named `origin`, then a push like the above
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attempts to update the `origin` branch in the shared repository from the
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developer's `origin` branch. The results may be unexpected, so it's
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usually best to remove any branch named `origin` from the shared
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repository.
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============
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Advanced Shared Repository Management
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-------------------------------------
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Git allows you to specify scripts called "hooks" to be run at certain
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points. You can use these, for example, to send all commits to the shared
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repository to a mailing list. See link:hooks.txt[Hooks used by git].
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You can enforce finer grained permissions using update hooks. See
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link:howto/update-hook-example.txt[Controlling access to branches using
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update hooks].
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CVS annotate
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||||
------------
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||||
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||||
Loading…
Reference in New Issue
Block a user