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Documentaiton (read-tree): update description of 3-way

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The merge-one-file used to leave the working tree intact, but
it has long been changed to leave the merge result there since
2a68a8659f commit.

Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Junio C Hamano 2005-12-05 23:26:10 -08:00
parent 5f6da1d9d2
commit bb6d7b893e
1 changed files with 31 additions and 12 deletions
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43
Documentation/git-read-tree.txt
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@ -167,20 +167,26 @@ $ git-read-tree -m <tree1> <tree2> <tree3>
and you will end up with an index with all of the <tree1> entries in and you will end up with an index with all of the <tree1> entries in
"stage1", all of the <tree2> entries in "stage2" and all of the "stage1", all of the <tree2> entries in "stage2" and all of the
<tree3> entries in "stage3". <tree3> entries in "stage3". When performing a merge of another
branch into the current branch, we use the common ancestor tree
as <tree1>, the current branch head as <tree2>, and the other
branch head as <tree3>.
Furthermore, `git-read-tree` has special-case logic that says: if you see Furthermore, `git-read-tree` has special-case logic that says: if you see
a file that matches in all respects in the following states, it a file that matches in all respects in the following states, it
"collapses" back to "stage0": "collapses" back to "stage0":
- stage 2 and 3 are the same; take one or the other (it makes no - stage 2 and 3 are the same; take one or the other (it makes no
difference - the same work has been done on stage 2 and 3) difference - the same work has been done on our branch in
stage 2 and their branch in stage 3)
- stage 1 and stage 2 are the same and stage 3 is different; take - stage 1 and stage 2 are the same and stage 3 is different; take
stage 3 (some work has been done on stage 3) stage 3 (our branch in stage 2 did not do anything since the
ancestor in stage 1 while their branch in stage 3 worked on
it)
- stage 1 and stage 3 are the same and stage 2 is different take - stage 1 and stage 3 are the same and stage 2 is different take
stage 2 (some work has been done on stage 2) stage 2 (we did something while they did nothing)
The `git-write-tree` command refuses to write a nonsensical tree, and it The `git-write-tree` command refuses to write a nonsensical tree, and it
will complain about unmerged entries if it sees a single entry that is not will complain about unmerged entries if it sees a single entry that is not
@ -223,11 +229,9 @@ populated. Here is an outline of how the algorithm works:
trivial rules .. trivial rules ..
You would normally use `git-merge-index` with supplied You would normally use `git-merge-index` with supplied
`git-merge-one-file` to do this last step. The script `git-merge-one-file` to do this last step. The script updates
does not touch the files in the work tree, and the entire merge the files in the working tree as it merges each path and at the
happens in the index file. In other words, there is no need to end of a successful merge.
worry about what is in the working directory, since it is never
shown and never used.
When you start a 3-way merge with an index file that is already When you start a 3-way merge with an index file that is already
populated, it is assumed that it represents the state of the populated, it is assumed that it represents the state of the
@ -238,7 +242,8 @@ merge refuses to run if it finds an entry in the original index
file that does not match stage 2. file that does not match stage 2.
This is done to prevent you from losing your work-in-progress This is done to prevent you from losing your work-in-progress
changes. To illustrate, suppose you start from what has been changes, and mixing your random changes in an unrelated merge
commit. To illustrate, suppose you start from what has been
commited last to your repository: commited last to your repository:
---------------- ----------------
@ -251,8 +256,8 @@ you notice that the tip of your "upstream" tree has advanced
since you pulled from him: since you pulled from him:
---------------- ----------------
$ git-fetch rsync://.... linus $ git-fetch git://.... linus
$ LT=`cat .git/MERGE_HEAD` $ LT=`cat .git/FETCH_HEAD`
---------------- ----------------
Your work tree is still based on your HEAD ($JC), but you have Your work tree is still based on your HEAD ($JC), but you have
@ -271,6 +276,20 @@ what you would commit is a pure merge between $JC and $LT without
your work-in-progress changes, and your work tree would be your work-in-progress changes, and your work tree would be
updated to the result of the merge. updated to the result of the merge.
However, if you have local changes in the working tree that
would be overwritten by this merge,`git-read-tree` will refuse
to run to prevent your changes from being lost.
In other words, there is no need to worry about what exists only
in the working tree. When you have local changes in a part of
the project that is not involved in the merge, your changes do
not interfere with the merge, and are kept intact. When they
*do* interfere, the merge does not even start (`git-read-tree`
complains loudly and fails without modifying anything). In such
a case, you can simply continue doing what you were in the
middle of doing, and when your working tree is ready (i.e. you
have finished your work-in-progress), attempt the merge again.
See Also See Also
-------- --------