$ git clone -n https://src.fedoraproject.org/rpms/ghc.git /var/lib/mock/f40-build-2698764-70098/root/chroot_tmpdir/scmroot/ghc
Cloning into '/var/lib/mock/f40-build-2698764-70098/root/chroot_tmpdir/scmroot/ghc'...
$ git fetch origin f352d5e70f441dd4e5194e2c8891937a68cb5037:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc
 * [new ref]         f352d5e70f441dd4e5194e2c8891937a68cb5037 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f352d5e fixup ghc-modern-c-fix patch file extension