$ git clone -n https://src.fedoraproject.org/rpms/ghc-libffi.git /var/lib/mock/f41-build-837639-159296/root/chroot_tmpdir/scmroot/ghc-libffi
Cloning into '/var/lib/mock/f41-build-837639-159296/root/chroot_tmpdir/scmroot/ghc-libffi'...
$ git fetch origin 02458b9f72b6a63158e28f3cfedadba297e5f2d1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-libffi
 * [new ref]         02458b9f72b6a63158e28f3cfedadba297e5f2d1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 02458b9 bump release