I did not manage to add myself to github-usernames.txt before the SVN repo was switched to read-only, and a mailing list post shows there are others in the same situation. Submitting a separate tracking issue for this case as it's a somewhat different issue from bug 43778, documenting the new commit access process for new users. In particular, there is a small and finite set of developers involved here.
I'm also an existing svn contributor that failed to add my name to the list. Tom Stellard sent me an email/link to correct things after I replied directly to this llvm-dev thread: http://lists.llvm.org/pipermail/llvm-dev/2019-October/136155.html
(In reply to Sanjay Patel from comment #1) Thank you for the link. Quoting here: > If you did not get a new invite, it might mean that you are already a 'Team > Member', you can check here: https://github.com/orgs/llvm/people to see if > you've already been added. > > Also, if you were an SVN committer and you still need commit access, please > email me off list with your svn and github IDs, and I'll get you added. This works as expected; I'll close this ticket in the near future unless someone is still unable to obtain access.
The near future has arrived!