Add option to change Master branch to Main

[Farnoosh63]

We would like to change our master branch on Github and would be great to have the option to set the default branch variable name. Thanks!

[stevector]

Hi @Farnoosh63, good idea! What happens when you try changing it now? Do builds on the main branch generate a ci- multidev rather than pushing to the Pantheon Dev environment?

If so, I think that the needed change might be in the underlying container where the $TERMINUS_ENV is derived: https://github.com/pantheon-systems/docker-build-tools-ci/blob/6.x/scripts/set-environment#L38 @sugaroverflow or @greg-1-anderson, what do you think?

[greg-1-anderson]

We could support a different default branch for Build Tools source repositories. We're not ready to do that for Pantheon repositories or upstream repositories yet, though.

[sugaroverflow]

+1 on supporting main as a default branch for Build Tools source repos (the project repo is already on main).

[rbvea]

FWIW, new repositories that are created through Github use main as the default branch now.

[jasonyarrington]

+1 on supporting main as a default branch for Build Tools source repos

[chachasikes]

master is still default branch for me (Pantheon default instance)

[aliciaj]

+1 on supporting main as a default branch