$ git clone -n https://src.fedoraproject.org/rpms/composer.git /var/lib/mock/f39-build-1457219-32971/root/chroot_tmpdir/scmroot/composer
Cloning into '/var/lib/mock/f39-build-1457219-32971/root/chroot_tmpdir/scmroot/composer'...
$ git fetch origin c2d8866cfc0a1d7e6824afc53165a9353abaa3a2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/composer
 * [new ref]         c2d8866cfc0a1d7e6824afc53165a9353abaa3a2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c2d8866 v2.6.5