Re: rename detection limit checking, cherry picking, and git am -3

From: Shawn O. Pearce <spearce@spearce.org>
Date: Sep 17, 2007, 03:47 UTC
Message-ID: <20070917034742.GG3099@spearce.org>
In-Reply-To: <46EDF54F.5030503@gmail.com>

Mark Levedahl <mlevedahl@gmail.com> wrote:

> The curious thing to me is the vast superiority of whatever 
> git-format-patch|git-am -3 does, and I wonder if that isn't a 
> fundementally better design for cherry picking than git-cherry-pick 
> implements (it obviously is for this case).

In this case `git am -3` creates a tree object containing only the files modified by the patch and then feeds that tree into git-merge-recursive. Now if you go study git-revert's code you'll see it actually just calls git-merge-recursive on three trees, but these are three complete trees.

So what's probably happening here is there's less candidates on one side in the `am -3` case, so we spend a lot less time generating the rename matrix, searching for a match, and we get better changes of finding a match.

I actually don't see why cherry-pick can't be defined in terms of `format-patch|am -3`. It probably would be faster in almost all cases.

-- 
Shawn.