Fix scrollbar in commit msg

[remique]

Fixes #350

Well I know that may not be the perfect solution, but a better fix itself would have to be inside scrollbar.rs anyway. This has to do with the way of how position of scrollbar is calculated, and changing max parameter of draw_scrollbar function would change nothing as either the scrollbar would never reach the end, or there would be a lot of empty lines.

This functionality would display scrollbar by default (which, regardless of this fix, is also the case with diff) and a simple check can prevent it from rendering.

What do you think?

[extrawurst]

@remique thanks for looking into this. it bugged me that this still felt like the wrong solution so I took a try on it: #388 - maybe you can play around with that to see how it works for you?

[extrawurst]

@remique sorry I did not want to demotivate you by taking a look myself :(

[remique]

@extrawurst No worries, you did not 👍 I had some last minute school stuff to resolve, so sorry for no response!

Also, this is still great learning experience for me=)