$ git clone -n https://src.fedoraproject.org/rpms/perl-XML-Fast.git /var/lib/mock/f41-build-816216-150052/root/chroot_tmpdir/scmroot/perl-XML-Fast
Cloning into '/var/lib/mock/f41-build-816216-150052/root/chroot_tmpdir/scmroot/perl-XML-Fast'...
$ git fetch origin 4faff07f3bcbf5d71a7f2b2b6522ea36d4c403c0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-XML-Fast
 * [new ref]         4faff07f3bcbf5d71a7f2b2b6522ea36d4c403c0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4faff07 Perl 5.40 rebuild