Improve running time

[fpvandoorn]

Two observations, potentially the same issue:

• Since using docgen-action, the total build time has increased significantly, from ~25 minutes to ~45 minutes in the Carleson project. Example: a run before docgen-action https://github.com/fpvandoorn/carleson/actions/runs/15597205228 and a run after docgen-action https://github.com/fpvandoorn/carleson/actions/runs/15611407268
  Building the docs & blueprint went from ~12 minutes to ~33 minutes
  This time is consistent between runs. It is possible that before docgen-action we turned off some option doc-gen that improved the building time before. However, I think that the next point is likely a large part of the culprit.

• The Mathlib docs are built every commit. Shouldn't they be cached? They were cached before. For example here is a random run from yesterday, and you can see that the docs are built for all Mathlib files: https://github.com/fpvandoorn/carleson/actions/runs/16600773795/job/46959517761

[Vierkantor]

Apologies for the late reply. This issue was caused by the action not caching the folder containing Mathlib docs (which is why we also see cache sizes in the order of a few KBs instead of multiple MBs). Commit 56dff2b should have fixed this. I opened a PR to update the action to a working version: fpvandoorn/carleson#501

[zabolotskii]

Any chance the documentation for Mathlib etc. can be omitted altogether, just building the docs for the project itself?

[Vierkantor]

Omitting documentation for other projects is something that we'd need to implement in doc-gen itself, and I expect it would cost some significant amount of effort to do so, unfortunately...