git: make dirstate status() respect matcher
As with other changes in this stack, we appear to have been getting
lucky in the past. An upcoming change behaved _very_ oddly without
this fix.
Differential Revision: https://phab.mercurial-scm.org/D8997
Greg Ward, author of the original bfiles extension
Na'Tosha Bard of Unity Technologies
Fog Creek Software
Special thanks to the University of Toronto and the UCOSP program