git diff

比较working tree和index

git diff [--] [<path>...]

比较working tree和指定commit

git diff <commit> [--] [<path>...]

比较index和指定commit

				git diff --cached <commit> [--] [<path>...] 

				git diff --staged <commit> [--] [<path>...]

比较commit和commit

git diff <commit> <commit> [--] [<path>...]