Make scrolling great again

[x80486]

Describe the Bug

Scrolling on Unstaged Changes (or Staged) sections is a little bit weird. For instance, with a long list of files, when you reach the bottom and try to go back the highlighted line doesn't go to the top to start scrolling again, but it goes with the list.

Notice the Diff section behaves as one would expect.

To Reproduce

Steps to reproduce the behavior:

1. Have a Git repo with a good amount of unstaged or staged files that will allow you to scroll
2. Press the Down arrow until the bottom is reached
3. Press the Up (several times)

Notice how the list moves with the press of every Up arrow along with the highlighted line, instead of just the highlighted line.

Expected Behavior

The list should stay in place until the top is reached, then it should move accordingly.

I filed this as a bug because the Diff section behaves correctly (for what I expect). This could have been an enhancement, or probably that's the intended behavior — in that case I would expect you to reconsider and possibly make it work like the Diff section!

Desktop

• OS: Arch Linux Linux uplink 5.4.46-1-lts #1 SMP Wed, 10 Jun 2020 20:36:34 +0000 x86_64 GNU/Linux
• Browser: N/A (why this matters anyway?)
• Version: gitui 0.7.0

[extrawurst]

@x80486 you are absolutely right, this can be improved!

followup to #52

[extrawurst]

@tisorlawan thanks again, this is released in 0.8 now: https://github.com/extrawurst/gitui/releases/tag/v0.8.0