$ git clone -n https://src.fedoraproject.org/forks/hypersa/rpms/ghc-tar.git /var/lib/mock/f39-build-2227215-53002/root/chroot_tmpdir/scmroot/ghc-tar
Cloning into '/var/lib/mock/f39-build-2227215-53002/root/chroot_tmpdir/scmroot/ghc-tar'...
$ git fetch origin 61d66de17bf14929577551e9f6546605aaf5d14b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/forks/hypersa/rpms/ghc-tar
 * [new ref]         61d66de17bf14929577551e9f6546605aaf5d14b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 61d66de rv64 rebuild