$ git clone -n https://src.fedoraproject.org/rpms/ghc-JuicyPixels.git /var/lib/mock/f41-build-839639-160289/root/chroot_tmpdir/scmroot/ghc-JuicyPixels
Cloning into '/var/lib/mock/f41-build-839639-160289/root/chroot_tmpdir/scmroot/ghc-JuicyPixels'...
$ git fetch origin ff3f9ba1e1709f2b80b489707b8d7326b8d8ab1b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-JuicyPixels
 * [new ref]         ff3f9ba1e1709f2b80b489707b8d7326b8d8ab1b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ff3f9ba https://hackage.haskell.org/package/JuicyPixels-3.3.9/changelog