Ah, thank you, I had not realized the default branch was already set on those organizations (I should have checked). That resolves my concern.

As things stand right now:

• This has been discussed in various forums, I think it's clear there's support for the principle.
• Given the disruption of the implementation and various other timescales, implementation may not actually happen until December timeframe but that's the way with RFCs anyway
• Orgs that manage their own build chains (like lsst-sqre) can transition ahead of time if they wish. 

Comments at variance with the above still welcome until RFC closes. 

I support this, and I think that asking all the DM developers to help out on a concentrated day of action (if helpful) is reasonable. If conda-forge can make the mega-migration then we can too! (see recent updates at https://github.com/conda-forge/conda-forge.github.io/issues/1162 ).

Can I request for a transition period, say a month or two, where both `master` and `main` branch names co-exist and the change of the default branch happens around the middle of this period? By this, I don't mean two different branches, but one single branch with an alias. I'm thinking along the lines of this Stack Overflow answer: https://stackoverflow.com/a/17236679

Unfortunately, git symbolic-ref main refs/heads/main may allow master to stay pointing to where main does, but my experiments seem to show that it is not the equivalent of a real branch, and commands do not work identically: e.g. git checkout master gives "detached HEAD" state, and I suspect merges will also be problematic. Also, I believe that the symbolic ref is only local to a clone; it does not seem possible to make it mandatory for all new clones.

If you are concerned about muscle memory typing the wrong branch name, you might try to use git checkout - or git switch - instead. It's shorter, and quite often what you want.