$ git clone -n https://src.fedoraproject.org/rpms/ghc-hakyll.git /var/lib/mock/f40-build-807737-145260/root/chroot_tmpdir/scmroot/ghc-hakyll
Cloning into '/var/lib/mock/f40-build-807737-145260/root/chroot_tmpdir/scmroot/ghc-hakyll'...
$ git fetch origin a3d57c48ae34d2583e6ebd348f6430a1d83f0bc4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-hakyll
 * [new ref]         a3d57c48ae34d2583e6ebd348f6430a1d83f0bc4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a3d57c4 rebuild