Merge branch 'baserock/jonathanmaw/S9007/upgrade-git' into baserock/morphbaserock/morph

Reviewed-by: Lars Wirzenius <lars.wirzenius@codethink.co.uk>
Reviewed-by: Daniel Silverstone <daniel.silverstone@codethink.co.uk>

1 files changed, 30 insertions, 2 deletions

diff --git a/mergetools/p4merge b/mergetools/p4merge
index 1a45c1b0c5..5a608abf9c 100644
--- a/mergetools/p4merge
+++ b/mergetools/p4merge
@@ -1,10 +1,38 @@
 diff_cmd () {
+	empty_file=
+
+	# p4merge does not like /dev/null
+	if test "/dev/null" = "$LOCAL"
+	then
+		LOCAL="$(create_empty_file)"
+	fi
+	if test "/dev/null" = "$REMOTE"
+	then
+		REMOTE="$(create_empty_file)"
+	fi
+
 	"$merge_tool_path" "$LOCAL" "$REMOTE"
+
+	if test -n "$empty_file"
+	then
+		rm -f "$empty_file"
+	fi
 }
 
 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
 }
+
+create_empty_file () {
+	empty_file="${TMPDIR:-/tmp}/git-difftool-p4merge-empty-file.$$"
+	>"$empty_file"
+
+	printf "%s" "$empty_file"
+}