$ git clone -n https://src.fedoraproject.org/rpms/perl-Math-Prime-XS.git /var/lib/mock/f45-build-24689-605/root/chroot_tmpdir/scmroot/perl-Math-Prime-XS
Cloning into '/var/lib/mock/f45-build-24689-605/root/chroot_tmpdir/scmroot/perl-Math-Prime-XS'...
$ git fetch origin 6847bceccd1900ae4f09ee7f3c4f1761ff6ad17c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Math-Prime-XS
 * [new ref]         6847bceccd1900ae4f09ee7f3c4f1761ff6ad17c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6847bce Perl 5.44 rebuild