cherry_pick_list: quit early if one side is empty

The --cherry-pick logic starts by counting the commits on each side,
so that it can filter away commits on the bigger one.  However, so
far it missed an opportunity for optimization: it doesn't need to do
any work if either side is empty.

This in particular helps the common use-case 'git rebase -i HEAD~$n':
it internally uses --cherry-pick, but since HEAD~$n is a direct
ancestor the left side is always empty.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/revision.c b/revision.c
index e75079a6e1316c74b4dff702170134dc7559898f..c2fad2fd7e7d83e3cd74faad34ba9427641bef50 100644 (file)
--- a/revision.c
+++ b/revision.c
@@ -514,6 +514,9 @@ static void cherry_pick_list(struct commit_list *list, struct rev_info *revs)
                        right_count++;
        }
 
+       if (!left_count || !right_count)
+               return;
+
        left_first = left_count < right_count;
        init_patch_ids(&ids);
        if (revs->diffopt.nr_paths) {