gg

now you can see the mental model of gg in the Wiki page

This version is a pre-release version and is ok to use (only tested in my computer with git 1.9.1), but now i have no time to write docs and do more tests. you can get the usage from the model: http://fmajor.lamost.org/blog/?p=1275, i will complete the doc and strengthen the stability in the feature.