When looking at the output of git absorb for more complex situations (i.e. more than just 1 or 2 hunks), the log gets quite noisy.

Instead of

Sep 10 17:05:18.741 INFO committed, header: +1,-1, commit: 50e4c58e0253c377d2cfcef4f1224c1f5e412060

a somewhat more useful info would be:

Sep 10 17:05:18.741 INFO committed 50e4c58e (+1,-1) to fixup 4711abcd: Some random commit that changed something

The proposed change includes:

1. Respect the core.abbrev setting of git
2. Providing commit that should be modified (machine-readable + human-friendly)