Add new ruleset, gitignore, with rules gitignore_required_patterns and gitignore_forbidden_patterns

[paulo-ferraz-oliveira]

It'll use files identified by dirs+filter (which should be .gitignore) and apply
(at the moment, the only existing) rule gitignore_patterns with the default value found in the documentation.

Closes #316.

Considerations

• rule name gitignore_patterns is up for discussion replace with two rules: required_patterns and forbidden_patterns
• config. option all_of (name and content) is up for discussion the option name shall be regexes
• ruleset name gitignore is up for discussion (though I'm rather fond of it)
• implementation in elvis_project elvis_gitignore is up for discussion (the implementation itself, too, but I'm talking more about the placement of the code)
• we may have to revisit the "since" once we discuss when to release stuff tentatively make it 4.0.0
• the need for further tests is up for discussion
• the error message is up for discussion

[elbrujohalcon]

Can we make two rules, as follows?

• required_patterns: for stuff that must be present in the file (i.e., the current rule)
• forbidden_patterns: for stuff that must not be present in the file (including, for instance, rebar.lock)?

And maybe we can put them in their own module (elvis_gitignore or something like that), instead of elvis_project?

[paulo-ferraz-oliveira]

Can we make two rules, as follows?

Why not options?

[paulo-ferraz-oliveira]

And maybe we can put them in their own module (elvis_gitignore or something like that)

rebar_config and elvis_config are part of "project", which is what this rule wants to be. Why should we separate into different files?

[elbrujohalcon]

Can we make two rules, as follows?

Why not options?

Mostly to have a ruleset with 2 rules, instead of one. 😜

[elbrujohalcon]

And maybe we can put them in their own module (elvis_gitignore or something like that)

rebar_config and elvis_config are part of "project", which is what this rule wants to be. Why should we separate into different files?

Fair enough. Let it be in elvis_project. :)

[paulo-ferraz-oliveira]

Brujo I think you need to update the settings for this

[paulo-ferraz-oliveira]

If it's not much, would you check the stuff above (initial description) that needs to be updated (?) - or maybe the checks are blocked to the author?

What's missing?

[elbrujohalcon]

I think I still prefer to have 2 rules: one for required patters and one for excluded patterns. In that case, I would call the option just patterns or (to match other rules) regexes.

[paulo-ferraz-oliveira]

We can go with two rules, sure. One's the mirror of the other one so duplicating code and tests + adjusting shouldn't take long.

[paulo-ferraz-oliveira]

I've updated the description: I'm gonna make it two rules, each with the same option name. And I'm tentatively saying "since" is 4.0.0.

[elbrujohalcon]

It's approved, @paulo-ferraz-oliveira … feel free to merge it whenever the checks are ✅

[paulo-ferraz-oliveira]

Good stuff. Thanks, @elbrujohalcon. Merging... (just gonna resolve the open conversations because of our rules to merge)