Manual:$wgGitInfoCacheDirectory

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Cache: $wgGitInfoCacheDirectory
Directory where GitInfo will look for pre-computed cache files.
Introduced in version:1.24.0 (Gerrit change 142319; git #b6d18ab9)
Removed in version:still in use
Allowed values:(absolute path) or false
Default value:false

DetailsEdit

Directory where GitInfo will look for pre-computed cache files. If false, the local directory of the MediaWiki component that is being checked for GitInfo will be used.

It's used to cache git information from MediaWiki core and extensions on Special:Version, if MediaWiki or extensions have been downloaded from git.