$ git clone -n https://src.fedoraproject.org/rpms/erlang-base64url.git /var/lib/mock/f41-build-side-1-2811234-32927/root/chroot_tmpdir/scmroot/erlang-base64url
Cloning into '/var/lib/mock/f41-build-side-1-2811234-32927/root/chroot_tmpdir/scmroot/erlang-base64url'...
$ git fetch origin 3181192c0b04945d821d89a21cd646b46c3c9beb:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/erlang-base64url
 * [new ref]         3181192c0b04945d821d89a21cd646b46c3c9beb -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3181192 Cosmetic changes