Show commit hashes in action summary

[maritaria]

Git management systems (github, gitlab, etc) often support referencing existing commits as part of issues, merges etc.

When finishing a feature it would be neat to get the commit hash of the created merge commit so you can share it easily with your peers.

Proposal

Summary of actions:
- The feature branch 'feature/xyz' was merged into 'develop'
- The merging commit is f356242{...}5459702cf
- Feature branch 'feature/xyz' has been removed
- You are now on branch 'develop'