$ git clone -n https://src.fedoraproject.org/rpms/ghc-hostname.git /var/lib/mock/f40-build-742185-110610/root/chroot_tmpdir/scmroot/ghc-hostname
Cloning into '/var/lib/mock/f40-build-742185-110610/root/chroot_tmpdir/scmroot/ghc-hostname'...
$ git fetch origin aca3863b926c3e749379a4a42294c968a5dcff75:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-hostname
 * [new ref]         aca3863b926c3e749379a4a42294c968a5dcff75 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at aca3863 bump release