$ git clone -n https://src.fedoraproject.org/rpms/glibmm2.4.git /var/lib/mock/f45-build-11174-428/root/chroot_tmpdir/scmroot/glibmm2.4
Cloning into '/var/lib/mock/f45-build-11174-428/root/chroot_tmpdir/scmroot/glibmm2.4'...
$ git fetch origin afefd20ed47b9db4f7decd8a2af581adb0cac5d5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/glibmm2.4
 * [new ref]         afefd20ed47b9db4f7decd8a2af581adb0cac5d5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at afefd20 Update to 2.66.10