Somehow it became a convention to split out tiny little snippets of PHP code from MediaWiki and make them top-level Gerrit projects. This seems like a really bad idea. Having a directory for PHP libraries would make them easier to find, and would make it possible for them to inherit permissions.
The following PHP libraries are top-level projects in Gerrit:
* CLDRPluralRuleParser
* IPSet
* RelPath
* RunningStat
* WrappedString
* at-ease
* avro-php
* base-convert
* cdb
* data-values
* php-session-serializer
* utfnormal
I suggest `mediawiki/libs`, by analogy with `mediawiki/php` and `mediawiki/services`, which are similarly products of the MediaWiki community which are not dependent on the MediaWiki core. JavaScript libraries like `unicodejs` could also go there.
I have heard that it is not easy to rename repositories in Gerrit. So we should make a container project as soon as possible, and put new libraries in it, so that the backlog for renaming does not continue to grow. We could also copy the affected repositories and make the old locations read-only.