查看某个文件的git 历史和更改

refs:
http://stackoverflow.com/questions/278192/view-the-change-history-of-a-file-using-git-versioning
git whatchanged -p filename

git log -p filename

You can also see when a specific line of code inside a file was changed with git blame filename. This will print out a short commit id, the author, timestamp, and complete line of code for every line in the file. This is very useful after you've found a bug
and you want to know when it was introduced (or who's fault it was).