$ git clone -n https://src.fedoraproject.org/rpms/ghc-pattern-arrows.git /var/lib/mock/f41-build-842723-161699/root/chroot_tmpdir/scmroot/ghc-pattern-arrows
Cloning into '/var/lib/mock/f41-build-842723-161699/root/chroot_tmpdir/scmroot/ghc-pattern-arrows'...
$ git fetch origin 298697a74858b501236d0e8e2608e72d813e9330:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-pattern-arrows
 * [new ref]         298697a74858b501236d0e8e2608e72d813e9330 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 298697a patch for mtl 2.3