$ git clone -n https://src.fedoraproject.org/rpms/ghc-vector-binary-instances.git /var/lib/mock/f39-build-2130988-50783/root/chroot_tmpdir/scmroot/ghc-vector-binary-instances
Cloning into '/var/lib/mock/f39-build-2130988-50783/root/chroot_tmpdir/scmroot/ghc-vector-binary-instances'...
$ git fetch origin ca7be83e2b4ccafdd72848c1d3a163470bb485e3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-vector-binary-instances
 * [new ref]         ca7be83e2b4ccafdd72848c1d3a163470bb485e3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ca7be83 revised .cabal file