From a discussion at T102614: Fix Generic.Files.LineLength errors in MediaWiki core by breaking long lines, it might be a good idea to not check the message files in languages/messages for Generic.Files.LineLength.
The annotated sample ruleset.xml has the example:
<!-- You can also hard-code ignore patterns for specific sniffs, a feature not available on the command line. Please note that all sniff-specific ignore patterns are checked using absolute paths. The code here will hide all messages from the Squiz DoubleQuoteUsage sniff for files that match either of the two exclude patterns. --> <rule ref="Squiz.Strings.DoubleQuoteUsage"> <exclude-pattern>*/tests/*</exclude-pattern> <exclude-pattern>*/data/*</exclude-pattern> </rule> <!-- You can also be more specific and just exclude some messages. Please note that all message-specific ignore patterns are checked using absolute paths. The code here will just hide the ContainsVar error generated by the Squiz DoubleQuoteUsage sniff for files that match either of the two exclude patterns. --> <rule ref="Squiz.Strings.DoubleQuoteUsage.ContainsVar"> <exclude-pattern>*/tests/*</exclude-pattern> <exclude-pattern>*/data/*</exclude-pattern> </rule>
We could update our ruleset.xml to do this, if there's consensus.