$ git clone -n https://src.fedoraproject.org/rpms/ghc-async.git /var/lib/mock/f39-build-1507298-35237/root/chroot_tmpdir/scmroot/ghc-async
Cloning into '/var/lib/mock/f39-build-1507298-35237/root/chroot_tmpdir/scmroot/ghc-async'...
$ git fetch origin 55b8a734f86e5ea69618e37481d18f598d40559a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-async
 * [new ref]         55b8a734f86e5ea69618e37481d18f598d40559a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 55b8a73 revised .cabal file