git diff 文件比较

1. git diff  filepath 工作区与暂存区比较
2. git diff HEAD filepath 工作区与HEAD ( 当前工作分支) 比较
3. git diff --staged 或 --cached  filepath 暂存区与HEAD比较
4. git diff branchName filepath  当前分支的文件与branchName 分支的文件进行比较
5. git diff commitId filepath 与某一次提交进行比较