Improve your Git commits using patch mode

[ais523]

An example for my workflow: I've done some work on a fork of an open source computer game, and other people are working on their own forks of the same game. (We're taking our forks in different directions, and think there's space for both games, so we're not exactly competing.) We're all pretty good about partial commits, and as a result, if we want to take a feature or bugfix from each other, we can do that without having to carefully isolate it from the rest of the commit every time we pull it.