$ git clone -n https://src.fedoraproject.org/rpms/firefox.git /var/lib/mock/f42-build-side-1-3586993-46927/root/chroot_tmpdir/scmroot/firefox
Cloning into '/var/lib/mock/f42-build-side-1-3586993-46927/root/chroot_tmpdir/scmroot/firefox'...
$ git fetch origin 3ef5a75841c4857a0eef004467116a2702f10488:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/firefox
 * [new ref]         3ef5a75841c4857a0eef004467116a2702f10488 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3ef5a75 Merge branch 'main' into f42