Set default branch name to "main" instead of "master".

[twoco]

Feature Description

When creating new repos, we should no longer use the word "master" for the branch. Just like GitHub and GitLab now use "main" instead of "master" as the default initial branch name.

https://sfconservancy.org/news/2020/jun/23/gitbranchname/

Screenshots

[jolheiser]

This is already configurable via DEFAULT_BRANCH.

[twoco]

But set to "master" per default, isn't it? I mean the initial value shipped from this software should be changed. Just a suggestion. But thanks for the hint.