Add cache for commit responses based on hashes

[thomas-boehm-tractive]

Commit information, identiefied by the has, does not change over time. Therefore, introduce a cache and add the information once it is retrieved first.

Your checklist for this pull request

• [x] Make sure you are requesting to pull a topic/feature/bugfix branch (right side) and not your master branch!
• [x] Ensure that the pull request title represents the desired changelog entry
• [x] Please describe what you did
• [x] Link to relevant issues in GitHub or in Jenkins JIRA
• [x] Link to relevant pull requests, esp. upstream and downstream changes
• [ ] Did you provide a test-case? That demonstrates feature works or fixes the issue.
  • No, as I am not sure how to write those.

Fixes #838

[lifeofguenter]

nice one @thomas-boehm-tractive !

thanks @KalleOlaviNiemitalo for having a look