$ git clone -n https://src.fedoraproject.org/rpms/virtualbox-guest-additions.git /var/lib/mock/f39-build-1572119-37783/root/chroot_tmpdir/scmroot/virtualbox-guest-additions
Cloning into '/var/lib/mock/f39-build-1572119-37783/root/chroot_tmpdir/scmroot/virtualbox-guest-additions'...
$ git fetch origin 694cdafbec993c9791486b15bd04714292d2778a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/virtualbox-guest-additions
 * [new ref]         694cdafbec993c9791486b15bd04714292d2778a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 694cdaf Update to 7.0.12 (#2244635)