Redesign the `git log` half-screen view

**Is your feature request related to a problem? Please describe.**
Instead of just having the `git log graph` to the left and the `diff` to the right, I would also want to see a `diff files` panel.

**Describe the solution you'd like**
The left panel could be split into an upper and lower half, where the upper one could show the `git log graph`, and the lower could show the `diff files`.

**Describe alternatives you've considered**
None, actually.

**Additional context**
Feast your eyes on this high quality prototype.