$ git clone -n https://src.fedoraproject.org/rpms/libmodulemd.git /var/lib/mock/f42-build-side-1-3584041-46891/root/chroot_tmpdir/scmroot/libmodulemd
Cloning into '/var/lib/mock/f42-build-side-1-3584041-46891/root/chroot_tmpdir/scmroot/libmodulemd'...
$ git fetch origin a0aae12009e5fbbe56fe8b9f3c4a1e4d5dcf0a33:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libmodulemd
 * [new ref]         a0aae12009e5fbbe56fe8b9f3c4a1e4d5dcf0a33 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a0aae12 2.15.2 bump