$ git clone -n https://src.fedoraproject.org/rpms/ghc-generic-deriving.git /var/lib/mock/f41-build-side-1-2811435-32930/root/chroot_tmpdir/scmroot/ghc-generic-deriving
Cloning into '/var/lib/mock/f41-build-side-1-2811435-32930/root/chroot_tmpdir/scmroot/ghc-generic-deriving'...
$ git fetch origin 4820a4af25974e4b8aaa142c3f87a96b3c1b750c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-generic-deriving
 * [new ref]         4820a4af25974e4b8aaa142c3f87a96b3c1b750c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4820a4a https://hackage.haskell.org/package/generic-deriving-1.14.5/changelog