Use-case:
We want to make it easier for all Wikimedia wikis to benefit from the great tools that are available, but that are (sadly) too often only added at the wikis who have many technically inclined editors. We should be making it easier to get tools like https://tools.wmflabs.org/langviews/ into the hands of smaller communities. And easier to deploy updates, if a standard URL is changed in the future.

Strings like [[MediaWiki:Sp-contributions-footer]] and [[MediaWiki:Histlegend]] are customized at some wikis, with useful tools that are only available to (some or all) Wikimedia projects - hence the strings cannot be mediawiki defaults, as they would not work in 3rd-party mediawiki installations, nor in some sister projects.

Detailed example:
That "langviews" example tool is currently linked, from some but not all of our projects, either

• at the top of the action=history pages, via the locally customized messages at [[MediaWiki:Histlegend]]
  • i.e. https://en.wikipedia.org/wiki/MediaWiki:Histlegend or https://fr.wikipedia.org/wiki/MediaWiki:Histlegend --
  • e.g. in-situ: https://en.wikipedia.org/w/index.php?title=Moon&action=history
• or, at the bottom of the action=info pages, via the locally customized messages at [[MediaWiki:Pageinfo-footer]]
  • i.e. https://en.wikipedia.org/wiki/MediaWiki:Pageinfo-footer or https://de.wikipedia.org/wiki/MediaWiki:Pageinfo-footer --
  • e.g. in-situ: https://en.wikipedia.org/w/index.php?title=Moon&action=info

Difficulty:
At first glance, the simplest/manual solution is to just encourage local customization.
The main problem with local customizations is: These will not show up for anyone who is using a non-default language preference. E.g. the customizations to Histlegend at Enwiki, will not be shown to anyone using a Dutch language preference: https://en.wikipedia.org/w/index.php?title=Foobar&action=history&uselang=nl
(Discussed in T50956: Can't override optional message in all languages with local customisation)

Questions/Hypotheses:
I think we want a few new translatable interface messages, e.g. [[MediaWiki:Wikimedia-Foo]], that are either:

1. only shown on all Wikimedia wikis
2. only shown on some Wikimedia wikis, e.g. just Wikipedias, and not other projects

Are there any technical solutions, for making a Mediawiki:String that is only shown on specific wiki groups? Is this what WikimediaMessages is for? (if so, how does it work? The docs are unclear)
Or are there alternative ways to approach this problem?

Prior discussion of two examples:

• T133292: Page view statistics link should be available in page information for all Wikimedia projects
• T67446: Figure out Wikimedia wikis' Special:Contributions footer (duplicative and difficult to maintain)

See also:

• T55921: Add message to provide useful links on Special:CentralAuth
• T129698: Example quarry query for searching multiple wikis for locally customized mediawiki:foo pages