It can be helpful to see the changes between two sets of code; git diff lets us do this by comparing two Git references and outputting the differences between them. In this lesson, we show how to use git diff along with the --stat, --cached, HEAD, origin/master, file(s)/dir(s) options.
If you want to see the difference between stagin area with last commit:
git diff --cached
See the all umcommit changes:
git diff HEAD
See the different with branch:
git diff origin/master //will show all the change which in local but not in remote master
Compare the file with remote branch:
git diff origin/master getRandomNumber.js // show the difference between local getRandomNumber.js file with remote master branch
[Practical Git] Compare file changes with git diff
原文：http://www.cnblogs.com/Answer1215/p/5763450.html