$ git clone -n https://src.fedoraproject.org/rpms/antlr4-project.git /var/lib/mock/f41-build-710661-13019/root/chroot_tmpdir/scmroot/antlr4-project
Cloning into '/var/lib/mock/f41-build-710661-13019/root/chroot_tmpdir/scmroot/antlr4-project'...
$ git fetch origin 6b6213bbc6f11e734e539b8f2129b69c206c73d1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/antlr4-project
 * [new ref]         6b6213bbc6f11e734e539b8f2129b69c206c73d1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6b6213b Add VCS field