$ git clone -n https://src.fedoraproject.org/rpms/ghc-stringbuilder.git /var/lib/mock/f39-build-2012042-45761/root/chroot_tmpdir/scmroot/ghc-stringbuilder
Cloning into '/var/lib/mock/f39-build-2012042-45761/root/chroot_tmpdir/scmroot/ghc-stringbuilder'...
$ git fetch origin c52a0d719713bfa4481ea5d5fe4d9d395df111ae:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-stringbuilder
 * [new ref]         c52a0d719713bfa4481ea5d5fe4d9d395df111ae -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c52a0d7 bump release