patchbomb: respect the `--git` option
I *think* this is the only diffopt exposed on the command line. TortoiseHg had
a similar issue creating diffopts, and this was caught by type hints in the next
commit.
import hashlib
try:
from ..thirdparty import sha1dc # pytype: disable=import-error
sha1 = sha1dc.sha1
except (ImportError, AttributeError):
sha1 = hashlib.sha1