$ git clone -n https://github.com/xcp-ng-rpms/createrepo_c.git /var/lib/mock/v8.3-incoming-10140-28716/root/chroot_tmpdir/scmroot/createrepo_c
Cloning into '/var/lib/mock/v8.3-incoming-10140-28716/root/chroot_tmpdir/scmroot/createrepo_c'...
$ git fetch origin fff051edcb7794a4a815bbb9fd4981a97f15468f:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/createrepo_c
 * [new ref]         fff051edcb7794a4a815bbb9fd4981a97f15468f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fff051e Import createrepo_c-0.21.1-3.xs8.src.rpm