Add support to multiroot workspace

[LeThiHyVong]

Issue Type: Feature Request

Well, I use your extension regularly. Currently, it only work on 1st project in workspace and I can't change/pick to another project at all. It's very troublesome if each project is a separated Git repo. There is no way I can create patch for each of them. So, could your please do something for this? Or at least, give the user a choice to switch between repos. Thanks.

Extension version: 0.2.1 VS Code version: Code 1.25.1 (1dfc5e557209371715f655691b1235b6b26a06be, 2018-07-11T15:43:11.471Z) OS version: Windows_NT ia32 6.1.7601

[paragdiwan]

Sure will take this up