Merge remote-tracking branch 'ko/maint' into jc/diff-index-quick-exit-early

* ko/maint: (4352 commits)
  git-submodule.sh: separate parens by a space to avoid confusing some shells
  Documentation/technical/api-diff.txt: correct name of diff_unmerge()
  read_gitfile_gently: use ssize_t to hold read result
  remove tests of always-false condition
  rerere.c: diagnose a corrupt MERGE_RR when hitting EOF between TAB and '\0'
  Git 1.7.5.3
  init/clone: remove short option -L and document --separate-git-dir
  do not read beyond end of malloc'd buffer
  git-svn: Fix git svn log --show-commit
  Git 1.7.5.2
  provide a copy of the LGPLv2.1
  test core.gitproxy configuration
  copy_gecos: fix not adding nlen to len when processing "&"
  Update draft release notes to 1.7.5.2
  Documentation/git-fsck.txt: fix typo: unreadable -> unreachable
  send-pack: avoid deadlock on git:// push with failed pack-objects
  connect: let callers know if connection is a socket
  connect: treat generic proxy processes like ssh processes
  sideband_demux(): fix decl-after-stmt
  t3503: test cherry picking and reverting root commits
  ...

Conflicts:
	diff.c

1 files changed, 104 insertions, 54 deletions

diff --git a/Documentation/git-read-tree.txt b/Documentation/git-read-tree.txt
index 7160fa1536..26fdadc642 100644
--- a/Documentation/git-read-tree.txt
+++ b/Documentation/git-read-tree.txt
@@ -8,7 +8,10 @@ git-read-tree - Reads tree information into the index
 
 SYNOPSIS
 --------
-'git read-tree' (<tree-ish> | [[-m [--trivial] [--aggressive] | --reset | --prefix=<prefix>] [-u | -i]] [--exclude-per-directory=<gitignore>] [--index-output=<file>] <tree-ish1> [<tree-ish2> [<tree-ish3>]])
+'git read-tree' [[-m [--trivial] [--aggressive] | --reset | --prefix=<prefix>]
+		[-u [--exclude-per-directory=<gitignore>] | -i]]
+		[--index-output=<file>] [--no-sparse-checkout]
+		(--empty | <tree-ish1> [<tree-ish2> [<tree-ish3>]])
 
 
 DESCRIPTION
@@ -22,8 +25,8 @@ 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.
 
 OPTIONS
 -------
@@ -54,13 +57,13 @@ OPTIONS
 	Show the progress of checking files out.
 
 --trivial::
-	Restrict three-way merge by 'git-read-tree' to happen
+	Restrict three-way merge by 'git read-tree' to happen
 	only if there is no file-level merging required, instead
 	of resolving merge for trivial cases and leaving
 	conflicting files unresolved in the index.
 
 --aggressive::
-	Usually a three-way merge by 'git-read-tree' resolves
+	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
@@ -107,13 +110,21 @@ OPTIONS
 	directories the index file and index output file are
 	located in.
 
+--no-sparse-checkout::
+	Disable sparse checkout support even if `core.sparseCheckout`
+	is true.
+
+--empty::
+	Instead of reading tree object(s) into the index, just empty
+	it.
+
 <tree-ish#>::
 	The id of the tree object(s) to be read/merged.
 
 
 Merging
 -------
-If `-m` is specified, 'git-read-tree' can perform 3 kinds of
+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.
@@ -121,18 +132,18 @@ provided.
 
 Single Tree Merge
 ~~~~~~~~~~~~~~~~~
-If only 1 tree is specified, 'git-read-tree' operates as if the user did not
+If only 1 tree is specified, 'git read-tree' operates as if the user did not
 specify `-m`, except that if the original index 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 match with the tree
 being read, the stat info from the index is used. (In other words, the
 index'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
-`git checkout-index -f -u -a`, the 'git-checkout-index' 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
-run after 'git-read-tree'.
+This is used to avoid unnecessary false hits when 'git diff-files' is
+run after 'git read-tree'.
 
 
 Two Tree Merge
@@ -141,46 +152,48 @@ Two Tree Merge
 Typically, this is invoked as `git read-tree -m $H $M`, where $H
 is the head commit of the current repository, and $M is the head
 of a foreign tree, which is simply ahead of $H (i.e. we are in a
-fast forward situation).
+fast-forward situation).
 
-When two trees are specified, the user is telling 'git-read-tree'
+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
-        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.
 
 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".
-Here are the "carry forward" rules:
+Here are the "carry forward" rules, where "I" denotes the index,
+"clean" means that index and work tree coincide, and "exists"/"nothing"
+refer to the presence of a path in the specified commit:
 
-        I (index)           H        M        Result
+	I                   H        M        Result
        -------------------------------------------------------
-      0 nothing             nothing  nothing  (does not happen)
-      1 nothing             nothing  exists   use M
-      2 nothing             exists   nothing  remove path from index
-      3 nothing             exists   exists,  use M if "initial checkout"
+     0  nothing             nothing  nothing  (does not happen)
+     1  nothing             nothing  exists   use M
+     2  nothing             exists   nothing  remove path from index
+     3  nothing             exists   exists,  use M if "initial checkout",
 				     H == M   keep index otherwise
-				     exists   fail
+				     exists,  fail
 				     H != M
 
         clean I==H  I==M
        ------------------
-      4 yes   N/A   N/A     nothing  nothing  keep index
-      5 no    N/A   N/A     nothing  nothing  keep index
+     4  yes   N/A   N/A     nothing  nothing  keep index
+     5  no    N/A   N/A     nothing  nothing  keep index
 
-      6 yes   N/A   yes     nothing  exists   keep index
-      7 no    N/A   yes     nothing  exists   keep index
-      8 yes   N/A   no      nothing  exists   fail
-      9 no    N/A   no      nothing  exists   fail
+     6  yes   N/A   yes     nothing  exists   keep index
+     7  no    N/A   yes     nothing  exists   keep index
+     8  yes   N/A   no      nothing  exists   fail
+     9  no    N/A   no      nothing  exists   fail
 
      10 yes   yes   N/A     exists   nothing  remove path from index
      11 no    yes   N/A     exists   nothing  fail
      12 yes   no    N/A     exists   nothing  fail
      13 no    no    N/A     exists   nothing  fail
 
-        clean (H=M)
+	clean (H==M)
        ------
      14 yes                 exists   exists   keep index
      15 no                  exists   exists   keep index
@@ -195,26 +208,26 @@ Here are the "carry forward" rules:
      21 no    yes   no      exists   exists   fail
 
 In all "keep index" cases, the index entry stays as in the
-original index file.  If the entry were not up to date,
-'git-read-tree' keeps the copy in the work tree intact when
+original index file.  If the entry is not up to date,
+'git read-tree' keeps the copy in the work tree intact when
 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 which of the "local changes" that you made were carried forward by running
 `git diff-index --cached $M`.  Note that this does not
-necessarily match `git diff-index --cached $H` would have
+necessarily match what `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
 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
 merge, but it would not show in `git diff-index --cached $M`
-output after two-tree merge.
+output after the two-tree merge.
 
-Case #3 is slightly tricky and needs explanation.  The result from this
+Case 3 is slightly tricky and needs explanation.  The result from this
 rule logically should be to remove the path if the user staged the removal
 of the path and then switching to a new branch.  That however will prevent
 the initial checkout from happening, so the rule is modified to use M (new
-tree) only when the contents of the index is empty.  Otherwise the removal
+tree) only when the content of the index is empty.  Otherwise the removal
 of the path is kept as long as $H and $M are the same.
 
 3-Way Merge
@@ -222,7 +235,7 @@ of the path is kept as long as $H and $M are the same.
 Each "index" entry has two bits worth of "stage" state. stage 0 is the
 normal one, and is the only one you'd see in any kind of normal use.
 
-However, when you do 'git-read-tree' with three trees, the "stage"
+However, when you do 'git read-tree' with three trees, the "stage"
 starts out at 1.
 
 This means that you can do
@@ -238,7 +251,7 @@ 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
 "collapses" back to "stage0":
 
@@ -254,7 +267,7 @@ a file that matches in all respects in the following states, it
    - stage 1 and stage 3 are the same and stage 2 is different take
      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
 stage 0.
 
@@ -270,7 +283,7 @@ 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
-  automatically collapse to "merged" state by '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
   will stay as separate entries in the index. It's up to "porcelain
@@ -294,8 +307,8 @@ populated.  Here is an outline of how the algorithm works:
     matching "stage1" entry if it exists too.  .. all the normal
     trivial rules ..
 
-You would normally use 'git-merge-index' with supplied
-'git-merge-one-file' to do this last step.  The script updates
+You would normally use 'git merge-index' with supplied
+'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.
 
@@ -317,7 +330,7 @@ $ JC=`git rev-parse --verify "HEAD^0"`
 $ git checkout-index -f -u -a $JC
 ----------------
 
-You do random edits, without running 'git-update-index'.  And then
+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:
 
@@ -343,34 +356,71 @@ 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
+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'
+*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.
 
 
+Sparse checkout
+---------------
+
+"Sparse checkout" allows to sparsely populate working directory.
+It uses skip-worktree bit (see linkgit:git-update-index[1]) to tell
+Git whether a file on working directory is worth looking at.
+
+"git read-tree" and other merge-based commands ("git merge", "git
+checkout"...) can help maintaining skip-worktree bitmap and working
+directory update. `$GIT_DIR/info/sparse-checkout` is used to
+define the skip-worktree reference bitmap. When "git read-tree" needs
+to update working directory, it will reset skip-worktree bit in index
+based on this file, which uses the same syntax as .gitignore files.
+If an entry matches a pattern in this file, skip-worktree will be
+set on that entry. Otherwise, skip-worktree will be unset.
+
+Then it compares the new skip-worktree value with the previous one. If
+skip-worktree turns from unset to set, it will add the corresponding
+file back. If it turns from set to unset, that file will be removed.
+
+While `$GIT_DIR/info/sparse-checkout` is usually used to specify what
+files are in. You can also specify what files are _not_ in, using
+negate patterns. For example, to remove file "unwanted":
+
+----------------
+*
+!unwanted
+----------------
+
+Another tricky thing is fully repopulating working directory when you
+no longer want sparse checkout. You cannot just disable "sparse
+checkout" because skip-worktree are still in the index and you working
+directory is still sparsely populated. You should re-populate working
+directory with the `$GIT_DIR/info/sparse-checkout` file content as
+follows:
+
+----------------
+*
+----------------
+
+Then you can disable sparse checkout. Sparse checkout support in "git
+read-tree" and similar commands is disabled by default. You need to
+turn `core.sparseCheckout` on in order to have sparse checkout
+support.
+
+
 SEE ALSO
 --------
 linkgit:git-write-tree[1]; linkgit:git-ls-files[1];
 linkgit:gitignore[5]
 
-
-Author
-------
-Written by Linus Torvalds <torvalds@osdl.org>
-
-Documentation
---------------
-Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>.
-
 GIT
 ---
 Part of the linkgit:git[1] suite