mailsplit: allow feeding mbox from standard input.

[git.git] / Documentation / git-read-tree.txt

diff --git a/Documentation/git-read-tree.txt b/Documentation/git-read-tree.txt
index 6440c4b..5653bac 100644 (file)
--- a/Documentation/git-read-tree.txt
+++ b/Documentation/git-read-tree.txt
@@ -9,16 +9,19 @@ git-read-tree - Reads tree information into the directory cache
 
 SYNOPSIS
 --------
 
 SYNOPSIS
 --------

-'git-read-tree' (<tree-ish> | -m <tree-ish1> [<tree-ish2> <tree-ish3>])"
+'git-read-tree' (<tree-ish> | [-m [-u|-i]] <tree-ish1> [<tree-ish2> [<tree-ish3>]])
+

 
 DESCRIPTION
 -----------
 
 DESCRIPTION
 -----------

-Reads the tree information given by <tree> into the directory cache,
+Reads the tree information given by <tree-ish> into the directory cache,

 but does not actually *update* any of the files it "caches". (see:
 but does not actually *update* any of the files it "caches". (see:

-git-checkout-cache)
+git-checkout-index)

 
 

-Optionally, it can merge a tree into the cache or perform a 3-way
-merge.
+Optionally, it can merge a tree into the cache, perform a
+fast-forward (i.e. 2-way) merge, or a 3-way merge, with the -m
+flag.  When used with -m, the -u flag causes it to also update
+the files in the work tree with the result of the merge.

 
 Trivial merges are done by "git-read-tree" itself.  Only conflicting paths
 will be in unmerged state when "git-read-tree" returns.
 
 Trivial merges are done by "git-read-tree" itself.  Only conflicting paths
 will be in unmerged state when "git-read-tree" returns.


@@ -26,7 +29,21 @@ will be in unmerged state when "git-read-tree" returns.
 OPTIONS
 -------
 -m::
 OPTIONS
 -------
 -m::

-       Perform a merge, not just a read
+       Perform a merge, not just a read.
+
+-u::
+       After a successful merge, update the files in the work
+       tree with the result of the merge.
+
+-i::
+       Usually a merge requires the index file as well as the
+       files in the working tree are up to date with the
+       current head commit, in order not to lose local
+       changes.  This flag disables the check with the working
+       tree and is meant to be used when creating a merge of
+       trees that are not directly related to the current
+       working tree status into a temporary index file.
+

 
 <tree-ish#>::
        The id of the tree object(s) to be read/merged.
 
 <tree-ish#>::
        The id of the tree object(s) to be read/merged.


@@ -34,20 +51,22 @@ OPTIONS
 
 Merging
 -------
 
 Merging
 -------

-If '-m' is specified, "git-read-tree" performs 2 kinds of merge, a single tree
-merge if only 1 tree is given or a 3-way merge if 3 trees are
+If '-m' is specified, "git-read-tree" can perform 3 kinds of
+merge, a single tree merge if only 1 tree is given, a
+fast-forward merge with 2 trees, or a 3-way merge if 3 trees are

 provided.
 
 provided.
 

+

 Single Tree Merge
 ~~~~~~~~~~~~~~~~~
 If only 1 tree is specified, git-read-tree operates as if the user did not
 specify '-m', except that if the original cache has an entry for a
 Single Tree Merge
 ~~~~~~~~~~~~~~~~~
 If only 1 tree is specified, git-read-tree operates as if the user did not
 specify '-m', except that if the original cache has an entry for a

-given pathname; and the contents of the path matches with the tree
+given pathname, and the contents of the path matches with the tree

 being read, the stat info from the cache is used. (In other words, the
 being read, the stat info from the cache is used. (In other words, the

-cache's stat()s take precedence over the merged tree's)
+cache's stat()s take precedence over the merged tree's).

 
 That means that if you do a "git-read-tree -m <newtree>" followed by a
 
 That means that if you do a "git-read-tree -m <newtree>" followed by a

-"git-checkout-cache -f -a", the "git-checkout-cache" only checks out
+"git-checkout-index -f -u -a", the "git-checkout-index" only checks out

 the stuff that really changed.
 
 This is used to avoid unnecessary false hits when "git-diff-files" is
 the stuff that really changed.
 
 This is used to avoid unnecessary false hits when "git-diff-files" is


@@ -65,10 +84,10 @@ fast forward situation).
 When two trees are specified, the user is telling git-read-tree
 the following:
 
 When two trees are specified, the user is telling git-read-tree
 the following:
 

-    (1) The current index and work tree is derived from $H, but
+     1. The current index and work tree is derived from $H, but

         the user may have local changes in them since $H;
 
         the user may have local changes in them since $H;
 

-    (2) The user wants to fast-forward to $M.
+     2. The user wants to fast-forward to $M.

 
 In this case, the "git-read-tree -m $H $M" command makes sure
 that no local change is lost as the result of this "merge".
 
 In this case, the "git-read-tree -m $H $M" command makes sure
 that no local change is lost as the result of this "merge".


@@ -117,13 +136,13 @@ operating under the -u flag.
 
 When this form of git-read-tree returns successfully, you can
 see what "local changes" you made are carried forward by running
 
 When this form of git-read-tree returns successfully, you can
 see what "local changes" you made are carried forward by running

-"git-diff-cache --cached $M".  Note that this does not
-necessarily match "git-diff-cache --cached $H" would have
+"git-diff-index --cached $M".  Note that this does not
+necessarily match "git-diff-index --cached $H" would have

 produced before such a two tree merge.  This is because of cases
 18 and 19 --- if you already had the changes in $M (e.g. maybe
 produced before such a two tree merge.  This is because of cases
 18 and 19 --- if you already had the changes in $M (e.g. maybe

-you picked it up via e-mail in a patch form), "git-diff-cache
+you picked it up via e-mail in a patch form), "git-diff-index

 --cached $H" would have told you about the change before this
 --cached $H" would have told you about the change before this

-merge, but it would not show in "git-diff-cache --cached $M"
+merge, but it would not show in "git-diff-index --cached $M"

 output after two-tree merge.
 
 
 output after two-tree merge.
 
 


@@ -166,23 +185,18 @@ merge. The different stages represent the "result tree" (stage 0, aka
 "merged"), the original tree (stage 1, aka "orig"), and the two trees
 you are trying to merge (stage 2 and 3 respectively).
 
 "merged"), the original tree (stage 1, aka "orig"), and the two trees
 you are trying to merge (stage 2 and 3 respectively).
 

-In fact, the way "git-read-tree" works, it's entirely agnostic about how
-you assign the stages, and you could really assign them any which way,
-and the above is just a suggested way to do it (except since
-"git-write-tree" refuses to write anything but stage0 entries, it makes
-sense to always consider stage 0 to be the "full merge" state).
-
-So what happens? Try it out. Select the original tree, and two trees
-to merge, and look how it works:
+The order of stages 1, 2 and 3 (hence the order of three
+<tree-ish> command line arguments) are significant when you
+start a 3-way merge with an index file that is already
+populated.  Here is an outline of how the algorithm works:

 
 - if a file exists in identical format in all three trees, it will
 
 - if a file exists in identical format in all three trees, it will

-  automatically collapse to "merged" state by the new git-read-tree.
+  automatically collapse to "merged" state by git-read-tree.

 
 - a file that has _any_ difference what-so-ever in the three trees
 
 - a file that has _any_ difference what-so-ever in the three trees

-  will stay as separate entries in the index. It's up to "script
+  will stay as separate entries in the index. It's up to "porcelain

   policy" to determine how to remove the non-0 stages, and insert a
   policy" to determine how to remove the non-0 stages, and insert a

-  merged version.  But since the index is always sorted, they're easy
-  to find: they'll be clustered together.
+  merged version.

 
 - the index file saves and restores with all this information, so you
   can merge things incrementally, but as long as it has entries in
 
 - the index file saves and restores with all this information, so you
   can merge things incrementally, but as long as it has entries in


@@ -201,15 +215,53 @@ to merge, and look how it works:
     matching "stage1" entry if it exists too.  .. all the normal
     trivial rules ..
 
     matching "stage1" entry if it exists too.  .. all the normal
     trivial rules ..
 

-Incidentally - it also means that you don't even have to have a
-separate subdirectory for this. All the information literally is in
-the index file, which is a temporary thing anyway. There is no need to
-worry about what is in the working directory, since it is never shown
-and never used.
+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.
+
+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
+files in your work tree, and you can even have files with
+changes unrecorded in the index file.  It is further assumed
+that this state is "derived" from the stage 2 tree.  The 3-way
+merge refuses to run if it finds an entry in the original index
+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:
+
+    $ JC=`cat .git/HEAD`
+    $ git-checkout-index -f -u -a $JC
+
+You do random edits, without running git-update-index.  And then
+you notice that the tip of your "upstream" tree has advanced
+since you pulled from him:
+
+    $ git-fetch rsync://.... linus
+    $ LT=`cat .git/MERGE_HEAD`
+
+Your work tree is still based on your HEAD ($JC), but you have
+some edits since.  Three-way merge makes sure that you have not
+added or modified cache entries since $JC, and if you haven't,
+then does the right thing.  So with the following sequence:
+
+    $ git-read-tree -m -u `git-merge-base $JC $LT` $JC $LT
+    $ git-merge-index git-merge-one-file -a
+    $ echo "Merge with Linus" | \
+      git-commit-tree `git-write-tree` -p $JC -p $LT
+
+what you would commit is a pure merge between $JC and LT without
+your work-in-progress changes, and your work tree would be
+updated to the result of the merge.
+

 
 See Also
 --------
 
 See Also
 --------

-link:git-write-tree.html[git-write-tree]; link:git-ls-files.html[git-ls-files]
+gitlink:git-write-tree[1]; gitlink:git-ls-files[1]

 
 
 Author
 
 
 Author


@@ -222,5 +274,5 @@ Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel
 
 GIT
 ---
 
 GIT
 ---

-Part of the link:git.html[git] suite
+Part of the gitlink:git[7] suite