$ git clone -n https://src.fedoraproject.org/rpms/cosmic-files.git /var/lib/mock/f41-build-side-1-3103838-39363/root/chroot_tmpdir/scmroot/cosmic-files
Cloning into '/var/lib/mock/f41-build-side-1-3103838-39363/root/chroot_tmpdir/scmroot/cosmic-files'...
$ git fetch origin 20a0199f06ad9a2b8fd68429f67ef0c997ed3451:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/cosmic-files
 * [new ref]         20a0199f06ad9a2b8fd68429f67ef0c997ed3451 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 20a0199 "Update to 1.0.0~alpha.3"