$ git clone -n https://src.fedoraproject.org/rpms/Rex.git /var/lib/mock/f42-build-3530725-46321/root/chroot_tmpdir/scmroot/Rex
Cloning into '/var/lib/mock/f42-build-3530725-46321/root/chroot_tmpdir/scmroot/Rex'...
$ git fetch origin 7f6aaa4dca29ed6d6ed37370721b37b7b628f54d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/Rex
 * [new ref]         7f6aaa4dca29ed6d6ed37370721b37b7b628f54d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7f6aaa4 Update to 1.16.0 (#2344047)