Add sniff and tests for concatenation operator spacing

[samwilson]

This change adds the ConcatenationSpacingSniff, which checks that the concatenation operator is correctly surrounded by spaces. Tests are also included.

The relevant WordPress coding standard reads: "Always put spaces after commas, and on both sides of logical, comparison, string and assignment operators."

Both the sniff and test classes are simply extensions of the Squiz.Strings.ConcatenationSpacing code (which kindly already supported the functionality we require here).

Refs #535.

[westonruter]

Humm. Looks like the tests fail only when the PHPCS_BRANCH is 2.2.0. Wonder why that is.

[samwilson]

Yes, I was just looking into that. I'm a bit confused so far though. Any ideas?

[samwilson]

Actually, scratch this whole thing. The right way to do this is perhaps to add the following to WordPress-Core/ruleset.xml —

<rule ref="Squiz.Strings.ConcatenationSpacing">
    <properties>
        <property name="spacing" value="1"/>
        <property name="ignoreNewlines" value="true"/>
    </properties>
</rule>

[samwilson]

Ok, I've updated the PR. I don't think there's any need to have tests for this, because the spacing behaviour is already tested in PHP_CodeSniffer.

[westonruter]

Perfect! 😍

[samwilson]

Thanks :)