Add configuration option to automatically collapse file diff when staging it

[yannxaver]

I expect the diff to automatically collapse when clicking on the stage button. If this is not desired as a default, it should be possible to configure it. Not having this configuration option effectively doubles the amount of clicks necessary when working through a change log.

[mkermani144]

I think most of the times we stage the files that we have checked, so we don't need to check them anymore, and auto-collapsing feature would help.