$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rabbit.git /var/lib/mock/f42-build-side-1-3579927-46816/root/chroot_tmpdir/scmroot/rubygem-rabbit
Cloning into '/var/lib/mock/f42-build-side-1-3579927-46816/root/chroot_tmpdir/scmroot/rubygem-rabbit'...
$ git fetch origin 9b6e18fceceee27798b531135d78f68e41f57fcc:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rabbit
 * [new ref]         9b6e18fceceee27798b531135d78f68e41f57fcc -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9b6e18f 3.0.5