Coala: Check invalid combinations of --ci, --format, and --json

[userzimmermann]

While reviewing https://github.com/coala/coala/pull/4036 , I realized that any combinations of --ci, --format, and --json are allowed for coala without any error. That's confusing. There is just a precedence for applying one of those flags and just ignoring the others:

--json
--format
--ci

coala --ci --format and coala --ci --json might be ok, but coala --format --json - which just ignores --format - definitely not.

@MariosPanag Interested? :)

CC @sils

[userzimmermann]

@Techievena This should be aligned with https://github.com/coala/coala/pull/3750 from @Nosferatul

[Nosferatul]

So, we want to warn users about using a combination of --ci, --format, and --json? @userzimmermann

[userzimmermann]

@Nosferatul Yes. Just like you did in https://github.com/coala/coala/pull/3750/files#diff-bad7250907d1790b012db412321e54c2R125 for coala --ci --format, whereby I'm not sure if --ci --format and --ci --json combinations are really worth an error, since --format and --json are non-interactive themselves. That needs to be discussed. But --format --json combination definitely needs that kind of error.

[Nosferatul]

well I could add that in my pr if that's ok, with you and @Techievena

[Techievena]

Yeah that's completely fine with me @Nosferatul You may add to your PR because you already have an open PR this stuff can happen much faster but the issue you're working upon will not be related to the PR.