SYNOPSIS
--------
-'git-read-tree' (<tree-ish> | [-m [-u|-i]] <tree-ish1> [<tree-ish2> [<tree-ish3>]])
+'git-read-tree' (<tree-ish> | [[-m [--aggressive] | --reset | --prefix=<prefix>] [-u | -i]] [--exclude-per-directory=<gitignore>] [--index-output=<file>] <tree-ish1> [<tree-ish2> [<tree-ish3>]])
DESCRIPTION
trees that are not directly related to the current
working tree status into a temporary index file.
+--aggressive::
+ Usually a three-way merge by `git-read-tree` resolves
+ the merge for really trivial cases and leaves other
+ cases unresolved in the index, so that Porcelains can
+ implement different merge policies. This flag makes the
+ command to resolve a few more cases internally:
++
+* when one side removes a path and the other side leaves the path
+ unmodified. The resolution is to remove that path.
+* when both sides remove a path. The resolution is to remove that path.
+* when both sides adds a path identically. The resolution
+ is to add that path.
+
+--prefix=<prefix>/::
+ Keep the current index contents, and read the contents
+ of named tree-ish under directory at `<prefix>`. The
+ original index file cannot have anything at the path
+ `<prefix>` itself, and have nothing in `<prefix>/`
+ directory. Note that the `<prefix>/` value must end
+ with a slash.
+
+--exclude-per-directory=<gitignore>::
+ When running the command with `-u` and `-m` options, the
+ merge result may need to overwrite paths that are not
+ tracked in the current branch. The command usually
+ refuses to proceed with the merge to avoid losing such a
+ path. However this safety valve sometimes gets in the
+ way. For example, it often happens that the other
+ branch added a file that used to be a generated file in
+ your branch, and the safety valve triggers when you try
+ to switch to that branch after you ran `make` but before
+ running `make clean` to remove the generated file. This
+ option tells the command to read per-directory exclude
+ file (usually '.gitignore') and allows such an untracked
+ but explicitly ignored file to be overwritten.
+
+--index-output=<file>::
+ Instead of writing the results out to `$GIT_INDEX_FILE`,
+ write the resulting index in the named file. While the
+ command is operating, the original index file is locked
+ with the same mechanism as usual. The file must allow
+ to be rename(2)ed into from a temporary file that is
+ created next to the usual index file; typically this
+ means it needs to be on the same filesystem as the index
+ file itself, and you need write permission to the
+ directories the index file and index output file are
+ located in.
+
<tree-ish#>::
The id of the tree object(s) to be read/merged.
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
-<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
a file that matches in all respects in the following states, it
"collapses" back to "stage0":
- 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 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 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
will complain about unmerged entries if it sees a single entry that is not
stage 0.
-Ok, this all sounds like a collection of totally nonsensical rules,
+OK, this all sounds like a collection of totally nonsensical rules,
but it's actually exactly what you want in order to do a fast
merge. The different stages represent the "result tree" (stage 0, aka
"merged"), the original tree (stage 1, aka "orig"), and the two trees
- the index file saves and restores with all this information, so you
can merge things incrementally, but as long as it has entries in
- stages 1/2/3 (ie "unmerged entries") you can't write the result. So
+ stages 1/2/3 (i.e., "unmerged entries") you can't write the result. So
now the merge algorithm ends up being really simple:
* you walk the index in order, and ignore all entries of stage 0,
trivial rules ..
You would normally use `git-merge-index` with supplied
-`git-merge-one-file` to do this last step. The script
-does not touch the files in the work tree, and the entire merge
-happens in the index file. In other words, there is no need to
-worry about what is in the working directory, since it is never
-shown and never used.
+`git-merge-one-file` to do this last step. The script updates
+the files in the working tree as it merges each path and at the
+end of a successful merge.
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
file that does not match stage 2.
This is done to prevent you from losing your work-in-progress
-changes. To illustrate, suppose you start from what has been
-commited last to your repository:
+changes, and mixing your random changes in an unrelated merge
+commit. To illustrate, suppose you start from what has been
+committed last to your repository:
----------------
$ JC=`git-rev-parse --verify "HEAD^0"`
since you pulled from him:
----------------
-$ git-fetch rsync://.... linus
-$ LT=`cat .git/MERGE_HEAD`
+$ git-fetch git://.... linus
+$ LT=`cat .git/FETCH_HEAD`
----------------
Your work tree is still based on your HEAD ($JC), but you have
your work-in-progress changes, and your work tree would be
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
--------