Please review: suggested final merge commit on the legacy repo

[Ulrich Spörlein]

Hi folks,
please have a look at the suggested merge commit, that merges master and 
main, which should allow folks that have significant work on the old 
hashes to:

  git remote add freebsd-legacy https://github.com/freebsd/freebsd-legacy.git && git fetch freebsd-legacy

  git merge freebsd-legacy/master  (this should work mostly conflict free
  git merge 3cc0c0d66a065554459bd2f9b4f80cc07426464a   (this is the main at the state of what legacy master is)

and then they have a shared ancestry (though twice the commits).

For rebase based workflows, rebasing onto legacy master should similarly 
work mostly conflict free, then they should be able to rebase onto 
3cc0c0d66a065554459bd2f9b4f80cc07426464a sans any conflicts and finally 
rebase onto freebsd/main with the usual set of newly introduced 
conflicts.

The wiki still needs updates to the final hashes now, something I'll do 
at some point.

Ideally, we can push this final commit to master before New Years and 
then we can start mirroring the new main/stable/releng into GH. master 
will be garbage collected at some future date.

I do not think doc and ports should receive similar treatments unless 
people can show me evidence that this is truly needed (and people can't 
figure this out from the provided instructions already).

Cheers
Uli