$ git clone -n https://src.fedoraproject.org/rpms/jxrlib.git /var/lib/mock/f45-build-14481-461/root/chroot_tmpdir/scmroot/jxrlib
Cloning into '/var/lib/mock/f45-build-14481-461/root/chroot_tmpdir/scmroot/jxrlib'...
$ git fetch origin 6bc34f7170b921da10100d345d27192dfac3bf45:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/jxrlib
 * [new ref]         6bc34f7170b921da10100d345d27192dfac3bf45 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6bc34f7 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild