Find a way to combine topological and chronological order

[mlange-42]

Problem:

• Commits should be in chronological order where possible (e.g. for synchronous work on multiple branches)
• Does not conform with "broken" chronolgy through rebase

How git handles it:

• git log shows chronological order, while
• git log --graph shows topological order

For some considerations on that, and an algorithm for "remporal tolopogical sort", see https://pvigier.github.io/2019/05/06/commit-graph-drawing-algorithms.html

Later discovered that crate git2 allows to combine sort orders:

walk.set_sorting(git2::Sort::TOPOLOGICAL | git2::Sort::TIME)?;

which may already be the solution, but needs to be tested

[mlange-42]

Solved through git2::Sort::TOPOLOGICAL | git2::Sort::TIME