[Misc #16671]
I'd like to bump it to 2.7 to use pattern matching in
tool/mk_builtin_loader.rb.
However, I experienced a few blockers. 2.5 seems like the closest
version that is easy enough to use on CIs, so let me bump the version to
it as an intermediate step for it. I want to use &. and <<~ in 2.3 too.
Known blockers:
* AppVeyor Visual Studio 2015 doesn't have Ruby 2.7. You'd need to bump
the version to Visual Studio 2019.
* GitHub Actions windows-2019 doesn't have Ruby 2.7 either. You
can use ruby/setup-ruby, but configure doesn't seem to work with it.
* For ruby/ruby-ci-imaage, bionic doesn't have Ruby 2.7. I tried using
ruby-build to build Ruby 2.7 from package, but the build on its CI
seems to somehow loop forever when I do that. So I gave it up for now.
We might want to wait until bionic becomes EOL.
Note:
* AppVeyor Visual Studio 2015 has Ruby <= 2.6.3
https://www.appveyor.com/docs/windows-images-software/#ruby
* GitHub Actions windows-2019 uses Ruby 2.5.9
https://github.com/actions/runner-images/blob/main/images/win/Windows2019-Readme.md
The command line arguments to `configure` are stored in `rbconfig.rb`.
Usually these are just useless but harmless after the installation,
however could affect unexpectedly when updating default gems.
Splits certain guidelines for singleton and instance method.
Calls for instance method to not prefix anything (like RDoc itself for a Ruby-coded instance method); e.g.:
count -> integer, not array.count,.
<=> other -> integer or nil, not hash <=> other -> integer or nil.
Groups previous guidelines into Arguments, Block, Return types, Aliases.
