$ git clone -n https://src.fedoraproject.org/rpms/rubygem-glib2.git /var/lib/mock/f41-build-808643-145985/root/chroot_tmpdir/scmroot/rubygem-glib2
Cloning into '/var/lib/mock/f41-build-808643-145985/root/chroot_tmpdir/scmroot/rubygem-glib2'...
$ git fetch origin 4ff91aa32e66bc70871efd884c5d4a4f04b5d1f5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-glib2
 * [new ref]         4ff91aa32e66bc70871efd884c5d4a4f04b5d1f5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4ff91aa 4.2.2 entry