common=$(git merge-base --all $head "$@")
        ;;
 *)
-       common=$(git show-branch --merge-base $head "$@")
+       common=$(git merge-base --all --octopus $head "$@")
        ;;
 esac
 echo "$head" >"$GIT_DIR/ORIG_HEAD"
 then
     if test "$allow_fast_forward" = "t"
     then
-        parents=$(git show-branch --independent "$head" "$@")
+       parents=$(git merge-base --independent "$head" "$@")
     else
-        parents=$(git rev-parse "$head" "$@")
+       parents=$(git rev-parse "$head" "$@")
     fi
     parents=$(echo "$parents" | sed -e 's/^/-p /')
     result_commit=$(printf '%s\n' "$merge_msg" | git commit-tree $result_tree $parents) || exit