Display diff in a preview pane upon selecting it

[joewiz]

Another suggestion borrowed from Git GUI clients such as GitHub Desktop and Tower:

Current behavior

To view a diff, the user must double-click on a changed file in the Working Copy view, which opens a new window with the diff. Then the user must close or move this window before being able to return to the main window

Proposal

Upon selecting (with a single click) a changed file in the Working Copy view, a preview of the diff should appear in a pane. This would allow a user to quickly preview the changes in a file before deciding whether to stage it.

A future enhancement would be to select lines within a diff to stage.

Here is screenshot taken from GitHub Desktop showing how selecting a changed file displays a preview of the diff: