mergetool: Add prompt to continue after failing to merge a file

This option stops git mergetool from aborting at the first failed merge.
After a failed merge the user will be prompted to indicated whether he
wishes to continue with attempting to merge subsequent paths or to
abort.

This allows some additional use patterns. Merge conflicts can now be
previewed one at time and merges can also be skipped so that they can be
performed in a later pass.

Signed-off-by: Charles Bailey <charles@hashpling.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-mergetool.sh

@@ -70,16 +70,16 @@ resolve_symlink_merge () {
 		git checkout-index -f --stage=2 -- "$MERGED"
 		git add -- "$MERGED"
 		cleanup_temp_files --save-backup
-		return
+		return 0
 		;;
 	    [rR]*)
 		git checkout-index -f --stage=3 -- "$MERGED"
 		git add -- "$MERGED"
 		cleanup_temp_files --save-backup
-		return
+		return 0
 		;;
 	    [aA]*)
-		exit 1
+		return 1
 		;;
 	    esac
 	done
@@ -97,15 +97,15 @@ resolve_deleted_merge () {
 	    [mMcC]*)
 		git add -- "$MERGED"
 		cleanup_temp_files --save-backup
-		return
+		return 0
 		;;
 	    [dD]*)
 		git rm -- "$MERGED" > /dev/null
 		cleanup_temp_files
-		return
+		return 0
 		;;
 	    [aA]*)
-		exit 1
+		return 1
 		;;
 	    esac
 	done
@@ -137,7 +137,7 @@ merge_file () {
 	else
 	    echo "$MERGED: file does not need merging"
 	fi
-	exit 1
+	return 1
     fi
 
     ext="$$$(expr "$MERGED" : '.*\(\.[^/]*\)$')"
@@ -269,7 +269,7 @@ merge_file () {
     if test "$status" -ne 0; then
 	echo "merge of $MERGED failed" 1>&2
 	mv -- "$BACKUP" "$MERGED"
-	exit 1
+	return 1
     fi
 
     if test "$merge_keep_backup" = "true"; then
@@ -280,6 +280,7 @@ merge_file () {
 
     git add -- "$MERGED"
     cleanup_temp_files
+    return 0
 }
 
 prompt=$(git config --bool mergetool.prompt || echo true)
@@ -350,6 +351,22 @@ init_merge_tool_path() {
 	fi
 }
 
+prompt_after_failed_merge() {
+    while true; do
+	printf "Continue merging other unresolved paths (y/n) ? "
+	read ans
+	case "$ans" in
+
+	    [yY]*)
+		return 0
+		;;
+
+	    [nN]*)
+		return 1
+		;;
+	esac
+    done
+}
 
 if test -z "$merge_tool"; then
     merge_tool=`git config merge.tool`
@@ -409,6 +426,8 @@ else
     fi
 fi
 
+last_status=0
+rollup_status=0
 
 if test $# -eq 0 ; then
     files=`git ls-files -u | sed -e 's/^[^	]*	//' | sort -u`
@@ -422,14 +441,29 @@ if test $# -eq 0 ; then
     sort -u |
     while IFS= read i
     do
+	if test $last_status -ne 0; then
+	    prompt_after_failed_merge < /dev/tty || exit 1
+	fi
 	printf "\n"
 	merge_file "$i" < /dev/tty > /dev/tty
+	last_status=$?
+	if test $last_status -ne 0; then
+	    rollup_status=1
+	fi
     done
 else
     while test $# -gt 0; do
+	if test $last_status -ne 0; then
+	    prompt_after_failed_merge || exit 1
+	fi
 	printf "\n"
 	merge_file "$1"
+	last_status=$?
+	if test $last_status -ne 0; then
+	    rollup_status=1
+	fi
 	shift
     done
 fi
-exit 0
+
+exit $rollup_status