[PATCH 2 of 2] diff: pass the diff matcher to the copy logic

[Durham Goode]

On 4/16/15 3:03 PM, Durham Goode wrote:
> # HG changeset patch
> # User Durham Goode <durham at fb.com>
> # Date 1429209108 25200
> #      Thu Apr 16 11:31:48 2015 -0700
> # Node ID 6b80abe8862ed1f637748f6f3710b4ec6326a35b
> # Parent  0270a44b46aabbaf794dbd62b08b622313fe1b85
> diff: pass the diff matcher to the copy logic
>
It was brought to my attention that the freeze has started.  Feel free 
to disregard this series if it doesn't qualify.  Though a 14s perf win 
might meet the bar.