$ git clone -n https://src.fedoraproject.org/rpms/chromium.git /var/lib/mock/f39-build-1976170-43332/root/chroot_tmpdir/scmroot/chromium
Cloning into '/var/lib/mock/f39-build-1976170-43332/root/chroot_tmpdir/scmroot/chromium'...
$ git fetch origin 199e1e8c0b2640c7bc42a220ac3e6036181c839a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/chromium
 * [new ref]         199e1e8c0b2640c7bc42a220ac3e6036181c839a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 199e1e8 update to 120.0.6099.62