In our CI we have a build against the main branch of GEOS. Currently, the cache does not work as intended.

The issue is as follows: for the main build, the ${{ github.workspace }}/geosinstall directory is cached under the cache key ${{ runner.os }}-geos-main. If there is a cache available, that whole directory is restored by GH actions, including geosinstall/rev.txt which contains the revision hash. If the current HEAD of GEOS does not agree, GEOS is rebuilt and the rev.txt updated. But then: the cache is not saved! So the cache remains at its original rev.txt which gets older until the cache is evicted (unsure what is the policy of that).

Glancing at the actions/cache docs, I don't think there is a way of forcing the adapted geosinstall to be cached. Maybe we could include the revision hash into the cache key.