Improve regex integration with DisableSyntax

[Jacoby6000]

I think the best way to see what I've changed is to look at the updated docs. To summarize:

1. Now error messages will underline the whole area of matched regex
2. The relevant capture group can be specified, in case you have complicated regex's which may match on parts which aren't helpful in the error message
3. scalafix errors which came from a regex match have access to the capture groups for substitution in the error messages.

I'm not dead set on any of the naming or formatting I've chosen. Feel free to have me change them

[Jacoby6000]

My current example is the magicNumber thing, and I don't like it. Just couldn't come up with a generic rule that has more complex regex.

[olafurpg]

This looks great @Jacoby6000 Thank you for this contribution! I left a few minor comments, otherwise great job 👍

[olafurpg]

s/simple//

[olafurpg]

To access to the capture groups of the regex use {$n} ...

[olafurpg]

Can we assert the contents of the message here?

 5 /* assert: DisableSyntax.magicNumbers
 ^
 Numbers (5 in this instance) should always ...
*/

See end of this section https://scalacenter.github.io/scalafix/docs/developers/tutorial.html#use-diagnostic-to-report-linter-errors

[Jacoby6000]

Thanks for the feedback. I believe I've addressed all the comments

[olafurpg]

LGTM 👍 I thought this has already been merged a long time ago, sorry for the slow response @Jacoby6000 I'm releasing a new version today with this change 😊