版本管理

工作区（Working Directory）：

就是电脑能看得到的目录，比如刚刚创建的learngit文件夹

版本库（Repository）：

工作区有一个隐藏目录.git，这个不算工作区，而是Git的版本库。

Git版本库中存了很多东西，其中最重要的就是叫Stage的暂存区，还有Git为我们创建的第一个分支master，以及指向master的一个指针——HEAD。

前面我们把文件往Git库添加的时候，是分两步执行的：

1. 用git add把文件添加进去，实际上是添加到暂存区；

2. 用git commit提交更改，实际上就是把暂存区的所有内容提交到当前分支。

g@g-PC MINGW64 /learngit (master)

$ vi readme.txt

g@g-PC MINGW64 /learngit (master)

$ cat readme.txt

Git is a distributed version control system.

Git is free software distributed under the GPL.

Git has a mutable index called stage.

g@g-PC MINGW64 /learngit (master)

$ touch LICENSE

 g@g-PC MINGW64 /learngit (master)

$ cat LICENSE

abc

g@g-PC MINGW64 /learngit (master)

$ git status # 查看状态

On branch master

Changes not staged for commit: # 修改了但未被提交

  (use "git add <file>..." to update what will be committed)

  (use "git checkout -- <file>..." to discard changes in working directory)

        modified:   readme.txt

Untracked files: # 没有被添加过 (Untracked : 无路径的;无脚印的,无足迹的) 

  (use "git add <file>..." to include in what will be committed)

        LICENSE

no changes added to commit (use "git add" and/or "git commit -a") # 没有更改且已被提交的文件 

g@g-PC MINGW64 /learngit (master)

$ git add readme.txt

g@g-PC MINGW64 /learngit (master)

$ git add LICENSE

warning: LF will be replaced by CRLF in LICENSE.

The file will have its original line endings in your working directory.

g@g-PC MINGW64 /learngit (master)

$ git status

On branch master

Changes to be committed:

  (use "git reset HEAD <file>..." to unstage)

        new file:   LICENSE

        new file:   biubiu

        modified:   readme.txt

g@g-PC MINGW64 /learngit (master)

$ git commit -m "undestand how stage work" # Git的提交，是一并全部提交，而不能单个提交

[master 50b7574] undestand how stage work

 3 files changed, 4 insertions(+), 1 deletion(-)

 create mode 100644 LICENSE

 create mode 100644 biubiu

g@g-PC MINGW64 /learngit (master)

$ git status # 此事的暂存区已经干干净净 working tree clean

On branch master

nothing to commit, working tree clean

git diff    #是工作区(work dict)和暂存区(stage)的比较

git diff --cached    #是暂存区(stage)和分支(master)的比较

在Git中，用HEAD表示当前版本，也就是最新的提交3628164...882e1e0（注意我的提交ID和你的肯定不一样），上一个版本就是HEAD^{，上上一个版本就是HEAD，当然往上100个版本写100个}比较容易数不过来，所以写成HEAD~100

g@g-PC MINGW64 /learngit (master)
$ cat readme.txt
Git is a distributed version control system.
Git is free software distributed under the GPL.
g@g-PC MINGW64 /learngit (master)
$ git reset --hard HEAD^ #回滚到上一个版本
HEAD is now at c3528d1 append GPL
g@g-PC MINGW64 /learngit (master)
$ cat readme.txt
Git is a version control system.
Git is free software.
Git is a distributed version control system.
Git is free software distributed under the GPL.


g@g-PC MINGW64 /learngit (master)
$ git reset --hard 932f121 #回滚到某一版本（版本号不用写全，Git会自动寻找）
HEAD is now at 932f121 del 2 rows
g@g-PC MINGW64 /learngit (master)
$ cat readme.txt
Git is a distributed version control system.
Git is free software distributed under the GPL.

查看命令历史，以便回过了之后到未来版本

g@g-PC MINGW64 /learngit (master)
$ git reflog
932f121 (HEAD -> master) HEAD@{0}: reset: moving to 932f121
c3528d1 HEAD@{1}: reset: moving to HEAD^
932f121 (HEAD -> master) HEAD@{2}: commit: del 2 rows
c3528d1 HEAD@{3}: commit: append GPL
311bbf5 HEAD@{4}: commit (initial): wrote a readme file