Test and document escaping on format!()

[novalis]

No description provided.

[alexcrichton]

This actually isn't entirely true. The # character also must be escaped (it's a back-reference to the currently-being-formatted argument in nested functions.

[alexcrichton]

That looks good to me. Two requests:

1. Could you squash these all into one commit?
2. While you're at it if you feel motivated, 'x' probably doesn't need the ' characters around the literal because it should already be separated as a small code block. Just a preference though, I don't mind either way.

[novalis]

Done.

In general, when editing pull requests to rust, should I squash as I go? Or does that get annoying for commenters whose comments get hidden away? (I'm happy to work either way; I just want to make everyone else happy too!)

[alexcrichton]

I don't think there's really a good convention on it one way or another. I've never been that impressed with github's code review tools. It's unfortunate that all history is lost in the github review if you rebase, but I generally think that it's fine to rebase.

Thankfully if you do comment on the commit itself github still marks the old comments with "show outdated diff", so at least there's a small consolation. If you comment on the overall pull request diff though I have absolutely no idea what github does to track those between revisions.

Anyway, thanks for putting up with me :)