$ git clone -n https://src.fedoraproject.org/rpms/glibmm2.68.git /var/lib/mock/f45-build-11170-428/root/chroot_tmpdir/scmroot/glibmm2.68
Cloning into '/var/lib/mock/f45-build-11170-428/root/chroot_tmpdir/scmroot/glibmm2.68'...
$ git fetch origin 9860229ad2a12a8068bac81670083b693d469e9d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/glibmm2.68
 * [new ref]         9860229ad2a12a8068bac81670083b693d469e9d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9860229 Update to 2.90.0