Cache ~/.m2/ to speed up GH actions

[fbricon]

No description provided.

[fbricon]

Before this change (in master)

After this change (building this PR)

So build time improvement ranges from 3 to 4 times faster, provided the cache can be reused (which will work most of the time, except if pom.xml or native-image.yaml changes)

[rgrunber]

Just curious about this value. Looking at https://docs.github.com/en/actions/guides/caching-dependencies-to-speed-up-workflows#matching-a-cache-key, this would match any cache key starting with ${{ runner.os }}-node and the most recent if there are multiple , but there aren't any that contain the "node" in the key declaration. Is it some pre-defined key somewhere else ?

[rgrunber]

@fbricon , I think this should just be ${{ runner.os }}- according to the docs. Let me know if that makes sense. I wouldn't mind trying this out on on JDT-LS as well.

[fbricon]

as per https://github.com/actions/cache/blob/main/examples.md#java---maven, it should actually be ${{ runner.os }}-maven

[rgrunber]

as per https://github.com/actions/cache/blob/main/examples.md#java---maven, it should actually be ${{ runner.os }}-maven

That's fine. So the key should be ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }} to match.

[fbricon]

Actually, we should split the cache in 2, for Maven and Graalvm, but I don't know what to use for graalvm restore key

[rgrunber]

Looks fine to me. We can hopefully take a similar approach in JDT-LS.