Merge branch 'kb/p4merge'

Adjust the order mergetools feeds the files to the p4merge backend
to match the p4 convention.

* kb/p4merge:
  merge-one-file: force content conflict for "both sides added" case
  git-merge-one-file: send "ERROR:" messages to stderr
  git-merge-one-file: style cleanup
  merge-one-file: remove stale comment
  mergetools/p4merge: create a base if none available
  mergetools/p4merge: swap LOCAL and REMOTE

Documentation/git-sh-setup.txt

@@ -82,6 +82,12 @@ get_author_ident_from_commit::
 	outputs code for use with eval to set the GIT_AUTHOR_NAME,
 	GIT_AUTHOR_EMAIL and GIT_AUTHOR_DATE variables for a given commit.
 
+create_virtual_base::
+	modifies the first file so only lines in common with the
+	second file remain. If there is insufficient common material,
+	then the first file is left empty. The result is suitable
+	as a virtual base input for a 3-way merge.
+
 GIT
 ---
 Part of the linkgit:git[1] suite

git-merge-one-file.sh

@@ -27,7 +27,7 @@ SUBDIRECTORY_OK=Yes
 cd_to_toplevel
 require_work_tree
 
-if ! test "$#" -eq 7
+if test $# != 7
 then
 	echo "$LONG_USAGE"
 	exit 1
@@ -38,7 +38,8 @@ case "${1:-.}${2:-.}${3:-.}" in
 # Deleted in both or deleted in one and unchanged in the other
 #
 "$1.." | "$1.$1" | "$1$1.")
-	if [ "$2" ]; then
+	if test -n "$2"
+	then
 		echo "Removing $4"
 	else
 		# read-tree checked that index matches HEAD already,
@@ -48,7 +49,8 @@ case "${1:-.}${2:-.}${3:-.}" in
 		# we do not have it in the index, though.
 		exec git update-index --remove -- "$4"
 	fi
-	if test -f "$4"; then
+	if test -f "$4"
+	then
 		rm -f -- "$4" &&
 		rmdir -p "$(expr "z$4" : 'z\(.*\)/')" 2>/dev/null || :
 	fi &&
@@ -67,7 +69,7 @@ case "${1:-.}${2:-.}${3:-.}" in
 	echo "Adding $4"
 	if test -f "$4"
 	then
-		echo "ERROR: untracked $4 is overwritten by the merge."
+		echo "ERROR: untracked $4 is overwritten by the merge." >&2
 		exit 1
 	fi
 	git update-index --add --cacheinfo "$7" "$3" "$4" &&
@@ -78,9 +80,10 @@ case "${1:-.}${2:-.}${3:-.}" in
 # Added in both, identically (check for same permissions).
 #
 ".$3$2")
-	if [ "$6" != "$7" ]; then
-		echo "ERROR: File $4 added identically in both branches,"
-		echo "ERROR: but permissions conflict $6->$7."
+	if test "$6" != "$7"
+	then
+		echo "ERROR: File $4 added identically in both branches," >&2
+		echo "ERROR: but permissions conflict $6->$7." >&2
 		exit 1
 	fi
 	echo "Adding $4"
@@ -95,71 +98,63 @@ case "${1:-.}${2:-.}${3:-.}" in
 
 	case ",$6,$7," in
 	*,120000,*)
-		echo "ERROR: $4: Not merging symbolic link changes."
+		echo "ERROR: $4: Not merging symbolic link changes." >&2
 		exit 1
 		;;
 	*,160000,*)
-		echo "ERROR: $4: Not merging conflicting submodule changes."
+		echo "ERROR: $4: Not merging conflicting submodule changes." >&2
 		exit 1
 		;;
 	esac
 
-	src2=`git-unpack-file $3`
+	src1=$(git-unpack-file $2)
+	src2=$(git-unpack-file $3)
 	case "$1" in
 	'')
 		echo "Added $4 in both, but differently."
-		# This extracts OUR file in $orig, and uses git apply to
-		# remove lines that are unique to ours.
-		orig=`git-unpack-file $2`
-		sz0=`wc -c <"$orig"`
-		@@DIFF@@ -u -La/$orig -Lb/$orig $orig $src2 | git apply --no-add
-		sz1=`wc -c <"$orig"`
-
-		# If we do not have enough common material, it is not
-		# worth trying two-file merge using common subsections.
-		expr $sz0 \< $sz1 \* 2 >/dev/null || : >$orig
+		orig=$(git-unpack-file $2)
+		create_virtual_base "$orig" "$src2"
 		;;
 	*)
 		echo "Auto-merging $4"
-		orig=`git-unpack-file $1`
+		orig=$(git-unpack-file $1)
 		;;
 	esac
 
-	# Be careful for funny filename such as "-L" in "$4", which
-	# would confuse "merge" greatly.
-	src1=`git-unpack-file $2`
 	git merge-file "$src1" "$orig" "$src2"
 	ret=$?
 	msg=
-	if [ $ret -ne 0 ]; then
+	if test $ret != 0 || test -z "$1"
+	then
 		msg='content conflict'
+		ret=1
 	fi
 
 	# Create the working tree file, using "our tree" version from the
 	# index, and then store the result of the merge.
 	git checkout-index -f --stage=2 -- "$4" && cat "$src1" >"$4" || exit 1
 	rm -f -- "$orig" "$src1" "$src2"
 
-	if [ "$6" != "$7" ]; then
-		if [ -n "$msg" ]; then
+	if test "$6" != "$7"
+	then
+		if test -n "$msg"
+		then
 			msg="$msg, "
 		fi
 		msg="${msg}permissions conflict: $5->$6,$7"
 		ret=1
 	fi
-	if [ "$1" = '' ]; then
-		ret=1
-	fi
 
-	if [ $ret -ne 0 ]; then
-		echo "ERROR: $msg in $4"
+	if test $ret != 0
+	then
+		echo "ERROR: $msg in $4" >&2
 		exit 1
 	fi
 	exec git update-index -- "$4"
 	;;
 
 *)
-	echo "ERROR: $4: Not handling case $1 -> $2 -> $3"
+	echo "ERROR: $4: Not handling case $1 -> $2 -> $3" >&2
 	;;
 esac
 exit 1

git-sh-setup.sh

@@ -249,6 +249,18 @@ clear_local_git_env() {
 	unset $(git rev-parse --local-env-vars)
 }
 
+# Generate a virtual base file for a two-file merge. Uses git apply to
+# remove lines from $1 that are not in $2, leaving only common lines.
+create_virtual_base() {
+	sz0=$(wc -c <"$1")
+	@@DIFF@@ -u -La/"$1" -Lb/"$1" "$1" "$2" | git apply --no-add
+	sz1=$(wc -c <"$1")
+
+	# If we do not have enough common material, it is not
+	# worth trying two-file merge using common subsections.
+	expr $sz0 \< $sz1 \* 2 >/dev/null || : >"$1"
+}
+
 
 # Platform specific tweaks to work around some commands
 case $(uname -s) in

mergetools/p4merge

@@ -21,8 +21,12 @@ diff_cmd () {
 
 merge_cmd () {
 	touch "$BACKUP"
-	$base_present || >"$BASE"
-	"$merge_tool_path" "$BASE" "$LOCAL" "$REMOTE" "$MERGED"
+	if ! $base_present
+	then
+		cp -- "$LOCAL" "$BASE"
+		create_virtual_base "$BASE" "$REMOTE"
+	fi
+	"$merge_tool_path" "$BASE" "$REMOTE" "$LOCAL" "$MERGED"
 	check_unchanged
 }