[PATCH] cherry_pick_list: quit early if one side is empty

[Thomas Rast <trast@student.ethz.ch>]

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>
---

On Saturday 20 February 2010 08:27:28 Jeff King wrote:
> 
> From my reading of the code, that is right, but this is the first time I
> ever looked at it, so who knows? :)

Junio agreed too, so here's a real patch.  To keep the complexity of
git-rebase--interactive from exploding even further, you can drop the
earlier one.

> Does it really make sense to treat binary files as anything other than a
> blob for generating patch id? That is, should we simply turn it into:
> 
>   binary diff
>   $from_sha1
>   $to_sha1
> 
> and hash that for the patch id?

I tend to agree, but I can't seem to find out what flags to flip :-(


 revision.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/revision.c b/revision.c
index 438cc87..29721ec 100644
--- a/revision.c
+++ b/revision.c
@@ -547,6 +547,9 @@ 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) {
-- 
1.7.0.139.gd1a75.dirty