Add rbs parse subcommand

[pocke]

This pull request will adds rbs check sub-command to check syntax error from .rbs files.

For example:

$ cat test.rbs
class C
  def foo: () ->
end

$ rbs check test.rbs
test.rbs:3:0: parse error on value: (kEND)

[soutaro]

The feature looks good. I'm wondering if there is a better name than rbs check.

• rbs parse
• rbs -C validate
• rbs syntax
• ... any other?

I don't think one of the above is better...

[pocke]

Hmm, I understand your concern.
I have the following ideas, but I'm not sure they are better.

• rbs syntax-check
• rbs syntax_check
• rbs validate

[soutaro]

I'd like to propose rbs parse. It parses the input and prints syntax errors if detected.

[pocke]

Sure! I renamed the command to rbs parse. 38e3692

[soutaro]

@pocke Thanks! 🎉