Print colored output only to a tty

[dohse]

Color output only if standard and error output are ttys.

[boneskull]

@dohse I can't imagine this works in a browser context.

[dohse]

The idea is from the reporter base. Does mocha.js run in browser context, but none of the reporters?

[dohse]

I changed this PR to only overwrite base reporter defaults when a color option is specified

[dasilvacontin]

@dohse, cool! Does checking for undefined/null in Mocha.prototype.useColors make sense? (and not setting anything in that case)

[dohse]

Yeah, it makes sense to set no option.

[dohse]

Ok, changed it to only set useColors in options if a flag is present.

[dasilvacontin]

@dohse, about reporters being used in the browser or not, I'm not sure right now. I've never used mocha in the browser, and I should look into that.

[dohse]

I doubt that reporters relying on the base reporter are running in the browser as they are already using tty.istty(). That might be different for the mocha main module.

[boneskull]

Hmm, sorry, I was confused about what I was looking at.

[dohse]

@boneskull I originally implemented the tty check in lib/mocha.js so your comment was right. The changed solution should address that.

Thanks for merging!