Fix `protocol_for_deps` allow for `git_subdir`'s `ref` and `tag`

[paulo-ferraz-oliveira]

Description

We:

• improve matching on branch for git_subdir
• identify raw resources with comments (so future-us knows where those references come from)
• allow for a new (though only for backwards compatibility) "with opts" match
  • it's unlikely it's commonly used, but since rebar3 supports it as legacy, I believe we should too.

Closes #370.

• [x] I have read and understood the contributing guidelines

[paulo-ferraz-oliveira]

I'm spelunking into the code: [0-9]+([.][0-9]+)*) was introduced in the regex in 0.2.9, but I'm still trying to find why (or what for).

Edit: oh, I think I see it... https://github.com/inaka/elvis_core/commit/12a966e537cd094560562da4056a17cdc150446c If we're still interested in supporting Erlang.mk we should keep it, but it needs to be updated; otherwise we can drop it.