1、简介
首先要知道3种状态：
-
working tree：就是在工作区进行修改，但没git add的那种状态
-
index file：工作区修改完以后使用了git add但没git commit的状态
-
commit：顾名思义，就是提交了（git commit了）
那现在再理解一下这三个指令的含义：
- git diff：比较working tree和index file的状态
- git diff HEAD：比较working tree和commit的状态
- git diff --cached：比较index和commit的状态
2、实例
比较git diff：
vim a.txt ==> 写a=1
vim b.txt ==> 写b=1
vim c.txt ==> 写c=1
#然后都git add .
#接着对a.txt进行修改 ==> 新增a=2
#输入git diff
$ git diff
warning: LF will be replaced by CRLF in a.txt.
The file will have its original line endings in your working directory
diff --git a/a.txt b/a.txt
index 73cdb8b..23d06d6 100644
--- a/a.txt
+++ b/a.txt
@@ -1 +1,2 @@
a=1
+a=2
比较git diff HEAD：
#把这些commit了，再重新创建个文件
git add .
git commit --amend
#接着对a.txt进行修改 ==> 新增a=3
git diff HEAD
比较git diff --cached
vim b.txt
git diff --cached
