Improve PR with automated tools

[farodin91]

Tools are we using or had used:

• codecov - https://codecov.io/gh/JanusGraph/janusgraph (mainly coverage)
• coverity - https://scan.coverity.com/projects/janusgraph-janusgraph (security focused, only manually)
• codacy - https://app.codacy.com/manual/JanusGraph/janusgraph/dashboard?branch=master (code quality checks)

New Tools

• lgtm - https://lgtm.com/projects/g/JanusGraph/janusgraph/?mode=list (small list of quality checks)
• codeql (internal security scan, see https://github.com/JanusGraph/janusgraph/security/code-scanning)

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Did I forgot anything? What do we want to do?

My Idea would be to activate codecov and lgtm in PRs.

[li-boxuan]

IIRC codacy was enabled before. I found it pretty useful. Did someone disable it?

lgtm looks similar to codacy. It seems codacy is more popular than lgtm.

I definitely vote for enabling codecov in PRs. I often visit the website and check coverage diff manually. Would be nice to see codecov diff in PR directly.

[farodin91]

@mbrukman Do you have admin rights in janusraph and codacy? Could you convert our codacy installation?

I think we(@porunov and I) are able to migrate codacy.

[li-boxuan]

Do we also consider checkstyle?

[farodin91]

Would be a good but they should be enforce also by standard editors such as VScode or Intellij.

[farodin91]

Codacy is back online.

[li-boxuan]

I just loosened the Codacy quality check requirement. Now it requires no major issue (previously it requires no minor issue).