1.git diff 查看文件内容不同

1.git diff filename 查看工作区和缓存区文件内容差异
2.git diff --cached fielname 查看缓存区和分支文件差异
3.git diff HEAD -- filename 查看工作区和分支文件内容差异

操作步骤：
1.新建一个new_file文件，第一次写入内容11111，git add到暂存区,git commit到分支master
2.再次编辑new_file文件，添加一行22222,再次git add到暂存区
3.最后再给new_file文件，添加一行33333,不做任何提交动作
4.我们来分别查看一下工作区、暂存区、分支上文件内容的差异

192:learn qingjiao$ cat new_file    #查看工作区文件内容
11111
22222
3333

192:learn qingjiao$ git diff  #查看此时工作区和缓存区内容区别
diff --git a/new_file b/new_file
index a5abd94..ae9f282 100644
--- a/new_file
+++ b/new_file
@@ -1,2 +1,3 @@
 11111
 22222
+3333  #工作区比缓存区文件内容多出此行

192:learn qingjiao$ git diff --cached #查看缓存区和分支文件差异
diff --git a/new_file b/new_file
index f7c6dd0..a5abd94 100644
--- a/new_file
+++ b/new_file
@@ -1 +1,2 @@
 11111
+22222  #缓存区比分支多出一行22222

192:learn qingjiao$ git diff HEAD -- new_file
 #第一次add后执行了一次commit操作，查看此时工作区和分支文件内容差异
diff --git a/new_file b/new_file
index f7c6dd0..ae9f282 100644
--- a/new_file
+++ b/new_file
@@ -1 +1,3 @@
 11111
+22222
+3333
#工作区比分支多出两行

2.git status 查看工作区状态

2.1 工作区存在待提交文件

qingjiao$ git status
On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

    modified:   readme.txt

no changes added to commit (use "git add" and/or "git commit -a")

2.2 git status 工作区无任何需提交文件

qingjiao$ git status
On branch master
nothing to commit, working tree clean

3.git log 查看文件历史commit日志

3.1 git log 原样输出文件提交日志

qingjiao$ git log readme.txt
commit 5947df380678bbc77a23bb770eac27a663b85d27 (HEAD -> master)
Author: = <907309377@qq.com>
Date:   Wed Aug 21 11:02:58 2019 +0800

    readme.txt文档中增加一行文字

commit fb7a039072f72684568844199dade1925d529688
Author: = <907309377@qq.com>
Date:   Tue Aug 20 21:33:47 2019 +0800

    first add readme.txt

3.2 加入参数--pretty=oneline 格式化输出提交日志

qingjiao$ git log --pretty=oneline
5947df380678bbc77a23bb770eac27a663b85d27 (HEAD -> master) readme.txt文档中增加一行文字
fb7a039072f72684568844199dade1925d529688 first add readme.txt