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

["Shawn O. Pearce" <spearce@spearce.org>]

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.