Add git-mergetool to run an appropriate merge conflict resolution program

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>

5 files changed, 405 insertions, 1 deletions

diff --git a/.gitignore b/.gitignore
index 0eaba0a27..27797d149 100644
--- a/.gitignore
+++ b/.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
diff --git a/Documentation/config.txt b/Documentation/config.txt
index 5408dd67d..aaae9ac30 100644
--- a/Documentation/config.txt
+++ b/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
diff --git a/Documentation/git-mergetool.txt b/Documentation/git-mergetool.txt
new file mode 100644
index 000000000..ae69a0eb8
--- /dev/null
+++ b/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
+
diff --git a/Makefile b/Makefile
index 1a51f84f5..45fe3663a 100644
--- a/Makefile
+++ b/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 \
diff --git a/git-mergetool.sh b/git-mergetool.sh
new file mode 100755
index 000000000..52386a544
--- /dev/null
+++ b/git-mergetool.sh
@@ -0,0 +1,352 @@
+#!/bin/sh
+#
+# This program resolves merge conflicts in git
+#
+# Copyright (c) 2006 Theodore Y. Ts'o
+#
+# This file is licensed under the GPL v2, or a later version
+# at the discretion of Junio C Hammano.
+#
+
+USAGE='[--tool=tool] [file to merge] ...'
+SUBDIRECTORY_OK=Yes
+. git-sh-setup
+require_work_tree
+
+# Returns true if the mode reflects a symlink
+function is_symlink () {
+    test "$1" = 120000
+}
+
+function local_present () {
+    test -n "$local_mode"
+}
+
+function remote_present () {
+    test -n "$remote_mode"
+}
+
+function base_present () {
+    test -n "$base_mode"
+}
+
+cleanup_temp_files () {
+    if test "$1" = --save-backup ; then
+	mv -- "$BACKUP" "$path.orig"
+	rm -f -- "$LOCAL" "$REMOTE" "$BASE"
+    else
+	rm -f -- "$LOCAL" "$REMOTE" "$BASE" "$BACKUP"
+    fi
+}
+
+function describe_file () {
+    mode="$1"
+    branch="$2"
+    file="$3"
+
+    echo -n "    "
+    if test -z "$mode"; then
+	echo -n "'$path' was deleted"
+    elif is_symlink "$mode" ; then
+	echo -n "'$path' is a symlink containing '"
+	cat "$file"
+	echo -n "'"
+    else
+	if base_present; then
+	    echo -n "'$path' was created"
+	else
+	    echo -n "'$path' was modified"
+	fi
+    fi
+    echo " in the $branch branch"
+}
+
+
+resolve_symlink_merge () {
+    while /bin/true; do
+	echo -n "Use (r)emote or (l)ocal, or (a)bort? "
+	read ans
+	case "$ans" in
+	    [lL]*)
+		git-checkout-index -f --stage=2 -- "$path"
+		git-add -- "$path"
+		cleanup_temp_files --save-backup
+		return
+		;;
+	   [rR]*)
+		git-checkout-index -f --stage=3 -- "$path"
+		git-add -- "$path"
+		cleanup_temp_files --save-backup
+		return
+		;;
+	    [qQ]*)
+		exit 1
+		;;
+	    esac
+	done
+}
+
+resolve_deleted_merge () {
+    while /bin/true; do
+	echo -n "Use (m)odified or (d)eleted file, or (a)bort? "
+	read ans
+	case "$ans" in
+	    [mM]*)
+		git-add -- "$path"
+		cleanup_temp_files --save-backup
+		return
+		;;
+	   [dD]*)
+		git-rm -- "$path"
+		cleanup_temp_files
+		return
+		;;
+	    [qQ]*)
+		exit 1
+		;;
+	    esac
+	done
+}
+
+merge_file () {
+    path="$1"
+
+    if test ! -f "$path" ; then
+	echo "$path: file not found"
+	exit 1
+    fi
+
+    f=`git-ls-files -u -- "$path"`
+    if test -z "$f" ; then
+	echo "$path: file does not need merging"
+	exit 1
+    fi
+
+    BACKUP="$path.BACKUP.$$"
+    LOCAL="$path.LOCAL.$$"
+    REMOTE="$path.REMOTE.$$"
+    BASE="$path.BASE.$$"
+
+    mv -- "$path" "$BACKUP"
+    cp -- "$BACKUP" "$path"
+
+    base_mode=`git ls-files -u -- "$path" | awk '{if ($3==1) print $1;}'`
+    local_mode=`git ls-files -u -- "$path" | awk '{if ($3==2) print $1;}'`
+    remote_mode=`git ls-files -u -- "$path" | awk '{if ($3==3) print $1;}'`
+
+    base_present   && git cat-file blob ":1:$path" > "$BASE" 2>/dev/null
+    local_present  && git cat-file blob ":2:$path" > "$LOCAL" 2>/dev/null
+    remote_present && git cat-file blob ":3:$path" > "$REMOTE" 2>/dev/null
+
+    if test -z "$local_mode" -o -z "$remote_mode"; then
+	echo "Deleted merge conflict for $path:"
+	describe_file "$local_mode" "local" "$LOCAL"
+	describe_file "$remote_mode" "remote" "$REMOTE"
+	resolve_deleted_merge
+	return
+    fi
+
+    if is_symlink "$local_mode" || is_symlink "$remote_mode"; then
+	echo "Symlink merge conflict for $path:"
+	describe_file "$local_mode" "local" "$LOCAL"
+	describe_file "$remote_mode" "remote" "$REMOTE"
+	resolve_symlink_merge
+	return
+    fi
+
+    echo "Normal merge conflict for $path:"
+    describe_file "$local_mode" "local" "$LOCAL"
+    describe_file "$remote_mode" "remote" "$REMOTE"
+    echo -n "Hit return to start merge resolution tool ($merge_tool): "
+    read ans
+
+    case "$merge_tool" in
+	kdiff3)
+	    if base_present ; then
+		(kdiff3 --auto --L1 "$path (Base)" -L2 "$path (Local)" --L3 "$path (Remote)" \
+		    -o "$path" -- "$BASE" "$LOCAL" "$REMOTE" > /dev/null 2>&1)
+	    else
+		(kdiff3 --auto -L1 "$path (Local)" --L2 "$path (Remote)" \
+		    -o "$path" -- "$LOCAL" "$REMOTE" > /dev/null 2>&1)
+	    fi
+	    status=$?
+	    if test "$status" -eq 0; then
+		rm "$BACKUP"
+	    fi
+	    ;;
+	tkdiff)
+	    if base_present ; then
+		tkdiff -a "$BASE" -o "$path" -- "$LOCAL" "$REMOTE"
+	    else
+		tkdiff -o "$path" -- "$LOCAL" "$REMOTE"
+	    fi
+	    status=$?
+	    if test "$status" -eq 0; then
+		mv -- "$BACKUP" "$path.orig"
+	    fi
+	    ;;
+	meld)
+	    touch "$BACKUP"
+	    meld -- "$LOCAL" "$path" "$REMOTE"
+	    if test "$path" -nt "$BACKUP" ; then
+		status=0;
+	    else
+		while true; do
+		    echo "$path seems unchanged."
+		    echo -n "Was the merge successful? [y/n] "
+		    read answer < /dev/tty
+		    case "$answer" in
+			y*|Y*) status=0; break ;;
+			n*|N*) status=1; break ;;
+		    esac
+		done
+	    fi
+	    if test "$status" -eq 0; then
+		mv -- "$BACKUP" "$path.orig"
+	    fi
+	    ;;
+	xxdiff)
+	    touch "$BACKUP"
+	    if base_present ; then
+		xxdiff -X --show-merged-pane \
+		    -R 'Accel.SaveAsMerged: "Ctrl-S"' \
+		    -R 'Accel.Search: "Ctrl+F"' \
+		    -R 'Accel.SearchForward: "Ctrl-G"' \
+		    --merged-file "$path" -- "$LOCAL" "$BASE" "$REMOTE"
+	    else
+		xxdiff -X --show-merged-pane \
+		    -R 'Accel.SaveAsMerged: "Ctrl-S"' \
+		    -R 'Accel.Search: "Ctrl+F"' \
+		    -R 'Accel.SearchForward: "Ctrl-G"' \
+		    --merged-file "$path" -- "$LOCAL" "$REMOTE"
+	    fi
+	    if test "$path" -nt "$BACKUP" ; then
+		status=0;
+	    else
+		while true; do
+		    echo "$path seems unchanged."
+		    echo -n "Was the merge successful? [y/n] "
+		    read answer < /dev/tty
+		    case "$answer" in
+			y*|Y*) status=0; break ;;
+			n*|N*) status=1; break ;;
+		    esac
+		done
+	    fi
+	    if test "$status" -eq 0; then
+		mv -- "$BACKUP" "$path.orig"
+	    fi
+	    ;;
+	emerge)
+	    if base_present ; then
+		emacs -f emerge-files-with-ancestor-command "$LOCAL" "$REMOTE" "$BASE" "$path"
+	    else
+		emacs -f emerge-files-command "$LOCAL" "$REMOTE" "$path"
+	    fi
+	    status=$?
+	    if test "$status" -eq 0; then
+		mv -- "$BACKUP" "$path.orig"
+	    fi
+	    ;;
+    esac
+    if test "$status" -ne 0; then
+	echo "merge of $path failed" 1>&2
+	mv -- "$BACKUP" "$path"
+	exit 1
+    fi
+    git add -- "$path"
+    cleanup_temp_files
+}
+
+while case $# in 0) break ;; esac
+do
+    case "$1" in
+	-t|--tool*)
+	    case "$#,$1" in
+		*,*=*)
+		    merge_tool=`expr "z$1" : 'z-[^=]*=\(.*\)'`
+		    ;;
+		1,*)
+		    usage ;;
+		*)
+		    merge_tool="$2"
+		    shift ;;
+	    esac
+	    ;;
+	--)
+	    break
+	    ;;
+	-*)
+	    usage
+	    ;;
+	*)
+	    break
+	    ;;
+    esac
+    shift
+done
+
+if test -z "$merge_tool"; then
+    merge_tool=`git-config merge.tool`
+    if test $merge_tool = kdiff3 -o $merge_tool = tkdiff -o \
+	$merge_tool = xxdiff -o $merge_tool = meld ; then
+	unset merge_tool
+    fi
+fi
+
+if test -z "$merge_tool" ; then
+    if type kdiff3 >/dev/null 2>&1 && test -n "$DISPLAY"; then
+	merge_tool="kdiff3";
+    elif type tkdiff >/dev/null 2>&1 && test -n "$DISPLAY"; then
+	merge_tool=tkdiff
+    elif type xxdiff >/dev/null 2>&1 && test -n "$DISPLAY"; then
+	merge_tool=xxdiff
+    elif type meld >/dev/null 2>&1 && test -n "$DISPLAY"; then
+	merge_tool=meld
+    elif type emacs >/dev/null 2>&1; then
+	merge_tool=emerge
+    else
+	echo "No available merge resolution programs available."
+	exit 1
+    fi
+fi
+
+case "$merge_tool" in
+    kdiff3|tkdiff|meld|xxdiff)
+	if ! type "$merge_tool" > /dev/null 2>&1; then
+	    echo "The merge tool $merge_tool is not available"
+	    exit 1
+	fi
+	;;
+    emerge)
+	if ! type "emacs" > /dev/null 2>&1; then
+	    echo "Emacs is not available"
+	    exit 1
+	fi
+	;;
+    *)
+	echo "Unknown merge tool: $merge_tool"
+	exit 1
+	;;
+esac
+
+if test $# -eq 0 ; then
+	files=`git ls-files -u | sed -e 's/^[^	]*	//' | sort -u`
+	if test -z "$files" ; then
+		echo "No files need merging"
+		exit 0
+	fi
+	echo Merging the files: $files
+	git ls-files -u | sed -e 's/^[^	]*	//' | sort -u | while read i
+	do
+		echo ""
+		merge_file "$i" < /dev/tty > /dev/tty
+	done
+else
+	while test $# -gt 0; do
+		echo ""
+		merge_file "$1"
+		shift
+	done
+fi
+exit 0