$ git clone -n https://src.fedoraproject.org/rpms/rubygem-poppler.git /var/lib/mock/f41-build-740683-13309/root/chroot_tmpdir/scmroot/rubygem-poppler
Cloning into '/var/lib/mock/f41-build-740683-13309/root/chroot_tmpdir/scmroot/rubygem-poppler'...
$ git fetch origin 53bfa23aed0befbf65359de1fc0dfed2af7a0ab7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-poppler
 * [new ref]         53bfa23aed0befbf65359de1fc0dfed2af7a0ab7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 53bfa23 4.2.2 entry