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
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.