Update git.txt

tools/git.txt

@@ -37,6 +37,8 @@ git diff <file>
 git diff HEAD -- <file>		查看工作区和版本库里面最新版本的区别
 git diff --check <file>     	检查是否有空白错误(regex:' \{1,\}$')
 git diff --cached <file>    	查看已add的内容(绿M)
+git diff branch1 branch2 --stat	查看两个分支差异
+git diff branch1 branch2 <file...> 查看分支文件具体差异
 
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 # 查看历史版本、历史操作