The current version of our Wikibase CodeSniffer rule set depends on mediawiki-codesniffer 0.8.1, which depends on php_codesniffer 2.9.0.
The next step is an update to mediawiki-codesniffer 0.9.0, which includes an update to php_codesniffer 3.0.1. This version contains changes that require us to rewrite our custom sniffs (that's not the hard part) and the test cases for them (that's the hard part).
From there on updates should be smoother.
This task also includes reviewing all sniffs that got added since mediawiki-codesniffer 0.9 and after, and carefully decide which should be enabled by default for all Wikibase code bases, and which should not. I will split sub-tickets of if necessary:
[x] Update custom test runner to work with php_codesniffer 3.x: https://github.com/wmde/WikibaseCodeSniffer/pull/16
[x] Review sniffs added in and update to mediawiki-codesniffer 0.9: https://github.com/wmde/WikibaseCodeSniffer/pull/16
From there, we are at 3.x, and all other updates are unrelated "bonuses" to this task:
[x] Review sniffs added in and update to mediawiki-codesniffer 0.10: https://github.com/wmde/WikibaseCodeSniffer/pull/17
[x] Review sniffs added in and update to mediawiki-codesniffer 0.11: https://github.com/wmde/WikibaseCodeSniffer/pull/18
[x] Review sniffs added in and update to mediawiki-codesniffer 0.12: https://github.com/wmde/WikibaseCodeSniffer/pull/19
[x] Review sniffs added in and update to mediawiki-codesniffer 13.0: https://github.com/wmde/WikibaseCodeSniffer/pull/20
[] Review sniffs added in and update to mediawiki-codesniffer 14.0: https://github.com/wmde/WikibaseCodeSniffer/pull/24
[] Review sniffs added in and update to mediawiki-codesniffer 15.0: https://github.com/wmde/WikibaseCodeSniffer/pull/24