Remove leading whitespace when doing line-comment

@justgook pointed out that the current behavior results in strange indentation when combined with how elm-format handles line comments. The IntelliJ default is to have the line comment start on the first column (far left edge). But elm-format doesn’t like that.

Here’s how the line commenter checks the preference in com.intellij.codeInsight.generation.CommentByLineCommentHandler:

CommonCodeStyleSettings languageSettings = CodeStyle.getLanguageSettings(psiFile, lineStartLanguage);
block.commentWithIndent = !languageSettings.LINE_COMMENT_AT_FIRST_COLUMN;

We should set LINE_COMMENT_AT_FIRST_COLUMN to false for all Elm code.

[klazuka]

I didn’t know about IndentedCommenter. That sounds like a good place to start.

My main requirement is that any comment inserted by IntelliJ round-trips nicely through elm-format. And it should look “reasonable” at each step.

So if I do:

1. cmd+/ (insert line comment)
2. run elm-format
3. do cmd+/ again on that line to uncomment

The code after each step should be formatted “reasonably”. It doesn’t mean that it has to be perfect, but it shouldn’t be terribly wrong either. And the final output after step 3 should (ideally) match the initial state before step 1 was performed. Obviously it can’t be totally reversible because elm-format tends to do crazy things with comments, but for most situations it should meet expectations.

So I would pick whichever option achieves the above goals and has the simplest implementation.

[klazuka]

Go for it. I don’t know offhand if there are any other issues that are better suited. This one shouldn’t be too hard, and I can help you if you have any questions.