tidy: exempt URLs from the line length restriction

[zackw]

The length of a URL is usually not under our control, and Markdown
provides no way to split a URL in the middle. Therefore, comment
lines consisting solely of a URL (possibly with a Markdown link
label in front) should be exempt from the line-length restriction.

Inline hyperlink destinations ( [foo](http://...) notation ) are
not exempt, because it is my arrogant opinion that long lines of
that type make the source text illegible.

The patch adds dependencies on the regex and lazy_static crates
to the tidy utility. This appears to Just Work, but if you would
rather not have that dependency I am willing to provide a hand-written
parser instead.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @aturon (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[steveklabnik]

This LGTM, but yeah, we're just getting to the place where we can use dependencies in places like this, see #39728 and #39633

/cc @rust-lang/compiler

[alexcrichton]

We don't really need lazy-static/regex for this, can we just ignore long lines with "http://" and "https://" ?

[steveklabnik]

Might need ../ too, maybe. Or we can cross that bridge if and when we come to it.

[zackw]

We don't really need lazy-static/regex for this, can we just ignore long lines with "http://" and "https://" ?

Well, that's essentially what I meant by a "hand-written parser", but I do think we should be a little more picky than just line.contains("http://") || line.contains("https://"). I got tripped up earlier by how permissive the parser for // ignore-tidy-foo is; currently style.rs is exempt from all of its own checks because contents.contains("ignore-tidy-whatever") matches itself!

... So anyway I wrote something, but it may not be the way someone 100% fluent in the language would write it, please tell me what you think.

[alexcrichton]

@bors: r+

Yeah this wasn't really written to be bulletproof, just catch some common mistakes.

[bors]

📌 Commit ff4758c has been approved by alexcrichton

[zackw]

@bors: retry