$ git clone -n https://src.fedoraproject.org/rpms/ghc-JuicyPixels.git /var/lib/mock/f40-build-2192222-51450/root/chroot_tmpdir/scmroot/ghc-JuicyPixels
Cloning into '/var/lib/mock/f40-build-2192222-51450/root/chroot_tmpdir/scmroot/ghc-JuicyPixels'...
$ git fetch origin 18ac404e1b0bc63f3489c88f5d999a87cd2cdb8e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-JuicyPixels
 * [new ref]         18ac404e1b0bc63f3489c88f5d999a87cd2cdb8e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 18ac404 https://hackage.haskell.org/package/JuicyPixels-3.3.8/changelog