$ git clone -n https://src.fedoraproject.org/rpms/ghc-tar.git /var/lib/mock/f41-build-837884-159471/root/chroot_tmpdir/scmroot/ghc-tar
Cloning into '/var/lib/mock/f41-build-837884-159471/root/chroot_tmpdir/scmroot/ghc-tar'...
$ git fetch origin 52851a04e6b28463175d2cae180b02bfaef6b62e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-tar
 * [new ref]         52851a04e6b28463175d2cae180b02bfaef6b62e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 52851a0 refresh .cabal revision