[PATCH 1 of 3 V3] dirstate: add prefix and suffix arguments to backup

[Yuya Nishihara]

On Fri, 13 May 2016 13:33:13 -0700, Mateusz Kwapich wrote:
> # HG changeset patch
> # User Mateusz Kwapich <mitrandir at fb.com>
> # Date 1463171289 25200
> #      Fri May 13 13:28:09 2016 -0700
> # Node ID 17853c3207bc004fb98dfb67c1a109c7de0b97e7
> # Parent  c641b8dfb98c2ade6995ba3aa341fe4d7b154827
> dirstate: add prefix and suffix arguments to backup

I couldn't find any problem, and our transaction guru said LGTM, so pushing
to the committed repo, thanks!