copies: respect narrowmatcher in "parent -> working dir" case
I don't know when this case happens and we don't seem to have tests
for it, but let's fix it anyway since I happened to notice it.
Differential Revision: https://phab.mercurial-scm.org/D5987
local test passed
addgroupcopy test passed
clone test passed
lowlevelcopy test passed
slicing test passed
issnapshot test passed
findsnapshot test passed