mergetools / p4mergeon commit push: teach --recurse-submodules the on-demand option (eb21c73)
   1diff_cmd () {
   2        "$merge_tool_path" "$LOCAL" "$REMOTE"
   3}
   4
   5merge_cmd () {
   6        touch "$BACKUP"
   7        $base_present || >"$BASE"
   8        "$merge_tool_path" "$BASE" "$LOCAL" "$REMOTE" "$MERGED"
   9        check_unchanged
  10}