Support --stdin-display-name and the mixed style of files and stdin

[Kuniwak]

Support --stdin-display-name and mixed style linting such as vint a.vim - b.vim (in commented at #240).

[blueyed]

Better:

You can see all available options by using --help:

[Kuniwak]

Fixed at 37a7e49.

[blueyed]

I do not find that name good.
What about --stdin-display-name? (used by flake8)

[Kuniwak]

I feel --stdin-display-name is a good name. Fixed at 7b718a5.

[blueyed]

I feel uneasy about the many changes.

Why is LintTargetFile required?

[blueyed]

Why?
Aren't we using pytest here?

[Kuniwak]

The reason why I remove py.test specific code is the learning cost and the debugging cost. I felt that keep time for implementation shorter was important because I had only few moments to implement it.

In this case, I forget sometimes how to use py.test, so the tests got failures by my mistakes. But understanding what the error messages meant and how to fix it were not easy to me. I think the reason why the error message is hard is that py.test using some magics to implement the parameterized testing feature.

But I do not mean py.test is unuseful for all situation. Only this case, I determined that py.test is unnecessary for me. Feel free to use py.test if using py.test is quick way to acheve what you want.

[Kuniwak]

I feel uneasy about the many changes.

I'm sorry about that. I was in hurry, so I could not separate changes.

Why is LintTargetFile required?

The reason is DRY. I found the following smells:

• Linter#lint_file and Linter#lint_text did almost same thing
• ProhibitMissingScriptEncoding#_check_stdin_has_multibyte_char and ProhibitMissingScriptEncoding#_check_file_has_multibyte_char did also same thing

There are 2 differences for each pair. The first one is what a file path is used. The second one is how to get the file content. We can unify the methods if we implement a new abstraction that encapsulate what a file path is holding and how to get the file content. This abstraction is AbstractLintTarget.

Additionally, I implemented CachedLintTarget to remove this TODO comment. ProhibitMissingScriptEncoding did read files or stdin again, so we can improve the performance by cacheing the content.