Misc #15843

Updated by k0kubun (Takashi Kokubun) about 1 year ago

## Background 

 * We're using `trunk` branch as a canonical development branch because it has been mirrored to there by git-svn. 
 * In a usual git repository, a HEAD branch is `master` by default. Using `trunk` instead of `master` is confusing and causes typo on git operations or typing git-related URLs. 
 * We can make an *alias branch* by using symbolic-ref on ``. We can start using `master` branch without disturbing any `trunk` usage. Why not use it? 

 ## Proposed schedule 

 * 2019 
   * 5/22: Announce this schedule 
   * 5/23: Make `master` symbolic-ref pointing to `trunk` on 
   * 5/23~6/30: Ask maintainers of CI (or whatever integrated with the repository) to explicitly use `master` branch instead of `trunk` at ruby-core mailing list. 
   * 7/1: Switch HEAD on from `trunk` to `master` (change the default branch of GitHub ruby/ruby to `master` too) 
 * 2020 
   * 1/1: Drop `trunk` branch on (`mv refs/heads/trunk refs/heads/master` at `/var/git/ruby.git`)