Works on wmflabs: https://en.wikipedia.beta.wmflabs.org/wiki/Special:Version - but that is synced to git.
I am not sure, if production is synced the same as labs.

See also T155624

There's also a few other bugs where we get weird edge cases, gitinfo not properly updated etc... IIRC, a full scap syncs it, sync-dir/sync-file doesn't, so hence, we get things out of skew

In my understanding, there are at least two different cases about why some extensions don’t have a Git hashes:

1. Some are registered as Composer library (e.g. DataValues* extensions installed with Semantic MediaWiki through Composer) and as such don’t appear because their code is in /vendor/X/Y instead of /extensions/Z; imho this is not a bug in MediaWiki core but either the extensions should be installed in /extensions either it should not be registered as a MediaWiki extension in Special:Version but as a Composer library (section above).
2. In some Git setup, particularly if a git gc ran in some directory, the class GitInfo class doesn’t read the file /.git/packed-refs and hence cannot retrieve the hash for this Git-versioned directory.

I prepare a patch for the second case.

Change 378223 had a related patch set uploaded (by Seb35; owner: Seb35):
[mediawiki/core@master] Improve GitInfo for reading packed refs

https://gerrit.wikimedia.org/r/378223

Change 378223 merged by jenkins-bot:
[mediawiki/core@master] Improve GitInfo for reading packed refs

https://gerrit.wikimedia.org/r/378223