1.本地分支追踪远程分支，从而可以直接输入git pull,git push 进行代码传输
http://stackoverflow.com/questions/520650/make-an-existing-git-branch-track-a-remote-branch
2.更改仓库地址
Instead of removing and re-adding, you can do this:
git remote set-url origin git://new.url.here
3.A gitignore file specifies intentionally untracked files that Git should ignore. Files already tracked by Git are not affected
