$ git clone -n https://src.fedoraproject.org/rpms/xml-security-c.git /var/lib/mock/f42-build-862927-171252/root/chroot_tmpdir/scmroot/xml-security-c
Cloning into '/var/lib/mock/f42-build-862927-171252/root/chroot_tmpdir/scmroot/xml-security-c'...
$ git fetch origin 6b201a7b7013a155e997e79a7661c912971d353d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xml-security-c
 * [new ref]         6b201a7b7013a155e997e79a7661c912971d353d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6b201a7 Rebuild for xerces-c 3.3