tig seem pretty close. Does everything except toggling "first-parent". I might implement that bit.

I don’t understand? It accepts all git-log(1) etc. arguments. `git --first-parent` for example. But I don’t see how to navigate from a merge commit to the second parent or something.

Yes, I've just discovered that in parallel. All I need for perfection is to be able to enable/disable that in the view dynamically (and the cursor stay in the same place).

But what's there is actually useful and I've installed tig properly now.