Add git-mergetool to run an appropriate merge conflict resolution pro…

…gram

The git-mergetool program can be used to automatically run an appropriate
merge resolution program to resolve merge conflicts.  It will automatically
run one of kdiff3, tkdiff, meld, xxdiff, or emacs emerge programs.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

.gitignore

@@ -75,6 +75,7 @@ git-merge-ours
 git-merge-recursive
 git-merge-resolve
 git-merge-stupid
+git-mergetool
 git-mktag
 git-mktree
 git-name-rev

Documentation/config.txt

@@ -453,6 +453,11 @@ merge.summary::
 	Whether to include summaries of merged commits in newly created
 	merge commit messages. False by default.
 
+merge.tool::
+	Controls which merge resolution program is used by
+	gitlink:git-mergetool[l].  Valid values are: "kdiff3", "tkdiff",
+	"meld", "xxdiff", "emerge"
+
 merge.verbosity::
 	Controls the amount of output shown by the recursive merge
 	strategy.  Level 0 outputs nothing except a final error

Documentation/git-mergetool.txt

@@ -0,0 +1,46 @@
+git-mergetool(1)
+================
+
+NAME
+----
+git-mergetool - Run merge conflict resolution tools to resolve merge conflicts
+
+SYNOPSIS
+--------
+'git-mergetool' [--tool=<tool>] [<file>]...
+
+DESCRIPTION
+-----------
+
+Use 'git mergetool' to run one of several merge utilities to resolve
+merge conflicts.  It is typically run after gitlink:git-merge[1].
+
+If one or more <file> parameters are given, the merge tool program will
+be run to resolve differences on each file.  If no <file> names are
+specified, 'git mergetool' will run the merge tool program on every file
+with merge conflicts.
+
+OPTIONS
+-------
+-t or --tool=<tool>::
+	Use the merge resolution program specified by <tool>.
+	Valid merge tools are:
+	kdiff3, tkdiff, meld, xxdiff, and emerge.
+
+	If a merge resolution program is not specified, 'git mergetool'
+	will use the configuration variable merge.tool.  If the
+	configuration variable merge.tool is not set, 'git mergetool'
+	will pick a suitable default.
+
+Author
+------
+Written by Theodore Y Ts'o <tytso@mit.edu>
+
+Documentation
+--------------
+Documentation by Theodore Y Ts'o.
+
+GIT
+---
+Part of the gitlink:git[7] suite
+

Makefile

@@ -179,7 +179,7 @@ SCRIPT_SH = \
 	git-clean.sh git-clone.sh git-commit.sh \
 	git-fetch.sh git-gc.sh \
 	git-ls-remote.sh \
-	git-merge-one-file.sh git-parse-remote.sh \
+	git-merge-one-file.sh git-mergetool.sh git-parse-remote.sh \
 	git-pull.sh git-rebase.sh \
 	git-repack.sh git-request-pull.sh git-reset.sh \
 	git-sh-setup.sh \