Add different verbosity levels

[mre]

More granular verbosity levels have been asked
for repeatedly.
To enable that we're moving to [env_logger] and [clap-verbosity-flag]
to provide more flexible verbosity settings.

Also tackles #661, #709.
Lays the groundwork for tackling #268 and #704.

https://github.com/rust-cli/env_logger
https://github.com/clap-rs/clap-verbosity-flag

[mre]

If someone finds the time I'd love to get a review to avoid regressions.

[tooomm]

Is there some brief explanation somewhere? Which information do the various level add (v) or remove (q)?

[mre]

At the moment it's pretty basic:

• Verbose mode (-v) prints data URLs and false-positive URLs (e.g. example.com, which is an IANA reserved domain).
• Normal mode (without any -v) skips those.

That's it.
We could add something to the docs, but I don't know if it's worth it. Suggestions welcome.

[tooomm]

Hmm, but what will -vv print then? Or -vvv?

Edit: I found some helpful comments in the code that have some more information: https://github.com/lycheeverse/lychee/blob/master/lychee-bin/src/verbosity.rs#L41-L46
From there, it also looks like -qq is not possible?

Ordinary users won't read the code. :)
Maybe the wordings on the command line parameters info can be tweaked a bit to give users some idea, without writing a full documentation.

[mre]

Hmm, but what will -vv print then? Or -vvv?

So far this is not used, but reserved for future use-cases. It is already supported by the crate we use for checking verbosity, so it was no extra work to include it.

From there, it also looks like -qq is not possible?

-qq is possible, but doesn't change much. So far not even -q is used as I don't have a good use-case for that in mind.

Maybe the wordings on the command line parameters info can be tweaked a bit to give users some idea, without writing a full documentation.

That's fair. I'm willing to accept pull requests to help increase the clarity. Would you be interested? Alternatively we could write something about it on the website.

[tooomm]

Thanks for your quick reply.
I can try to circle back to it during the holidays. 👍