diff --git a/mergetools/opendiff b/mergetools/opendiff
--- /dev/null
+++ b/mergetools/opendiff
@@ -0,0 +1,16 @@
+diff_cmd () {
+ "$merge_tool_path" "$LOCAL" "$REMOTE" | cat
+}
+
+merge_cmd () {
+ touch "$BACKUP"
+ if $base_present
+ then
+ "$merge_tool_path" "$LOCAL" "$REMOTE" \
+ -ancestor "$BASE" -merge "$MERGED" | cat
+ else
+ "$merge_tool_path" "$LOCAL" "$REMOTE" \
+ -merge "$MERGED" | cat
+ fi
+ check_unchanged
+}