$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rugged.git /var/lib/mock/f40-build-733998-105650/root/chroot_tmpdir/scmroot/rubygem-rugged
Cloning into '/var/lib/mock/f40-build-733998-105650/root/chroot_tmpdir/scmroot/rubygem-rugged'...
$ git fetch origin ffdfefb3c1bf29ce32aba8c3d8b390d1cb873517:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rugged
 * [new ref]         ffdfefb3c1bf29ce32aba8c3d8b390d1cb873517 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ffdfefb Update to 1.7.1 (rhbz#2237289)