创建ssh key

$ ssh-keygen -t rsa -C "youremail@example.com"
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更新仓库

$ git push origin master
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新建/修改文件

新建文件和修改文件都是在git仓库目录下进行的，如果是新建就将新建的文件放到git仓库目录，修改则直接在文件上进行修改，例如：

我们编写一个readme.txt文件，内容如下：

Git is a version control system.
Git is free software.
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让后放到git目录下，然后使用git add指令添加，修改也是这个指令

$ git add readme.txt
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然后用commit提交修改

$ git commit -m "wrote a readme file"
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这时我们对readme文件进行修改

Git is a distributed version control system.
Git is free software.
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然后可以用git status查看状态

$ 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")
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上面的输出告诉我们，readme被修改了，但是还没提交
我们可以用git diff查看修改了什么

$ git diff readme.txt 
diff --git a/readme.txt b/readme.txt
index 46d49bf..9247db6 100644
--- a/readme.txt
+++ b/readme.txt
@@ -1,2 +1,2 @@
-Git is a version control system.
+Git is a distributed version control system.
 Git is free software.
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然后我们重复之前的操作就可以提交修改了

$ git add readme.txt
$ git commit -m "add distributed"
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这时我们再进行修改，将readme改为

Git is a distributed version control system.
Git is free software distributed under the GPL.
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然后提交

$ git add readme.txt
$ git commit -m "append GPL"
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查看log

使用git log命令可以查看历史修改信息

$ git log
commit 1094adb7b9b3807259d8cb349e7df1d4d6477073 (HEAD -> master)
Author: Michael Liao <askxuefeng@gmail.com>
Date:   Fri May 18 21:06:15 2018 +0800

    append GPL

commit e475afc93c209a690c39c13a46716e8fa000c366
Author: Michael Liao <askxuefeng@gmail.com>
Date:   Fri May 18 21:03:36 2018 +0800

    add distributed

commit eaadf4e385e865d25c48e7ca9c8395c3f7dfaef0
Author: Michael Liao <askxuefeng@gmail.com>
Date:   Fri May 18 20:59:18 2018 +0800

    wrote a readme file
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使用–pretty=oneline减少输出信息

$ git log --pretty=oneline
1094adb7b9b3807259d8cb349e7df1d4d6477073 (HEAD -> master) append GPL
e475afc93c209a690c39c13a46716e8fa000c366 add distributed
eaadf4e385e865d25c48e7ca9c8395c3f7dfaef0 wrote a readme file
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前面的长串是版本号
HEAD表示最新版本，HEAD^ 表示上一个版本，HEAD^^ 表示上上个版本，往上很多版本比如100可以写为HEAD~100

版本回退

使用git reset 可以实现版本回退

$ git reset --hard HEAD^
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这时我们再看log就会变化了

$ git log
commit e475afc93c209a690c39c13a46716e8fa000c366 (HEAD -> master)
Author: Michael Liao <askxuefeng@gmail.com>
Date:   Fri May 18 21:03:36 2018 +0800

    add distributed

commit eaadf4e385e865d25c48e7ca9c8395c3f7dfaef0
Author: Michael Liao <askxuefeng@gmail.com>
Date:   Fri May 18 20:59:18 2018 +0800

    wrote a readme file
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如果我们想反悔的话，可以使用git reflog查看之前的操作，找到想要返回的版本号就行

$ git reflog
e475afc HEAD@{1}: reset: moving to HEAD^
1094adb (HEAD -> master) HEAD@{2}: commit: append GPL
e475afc HEAD@{3}: commit: add distributed
eaadf4e HEAD@{4}: commit (initial): wrote a readme file
$ git reset --hard 1094a
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丢弃工作区的修改

使用 git checkout

$ git checkout -- readme.txt
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丢弃暂存区的修改

$ git reset HEAD readme.txt
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文件的删除

$ git rm test.txt
$ git commit -m "remove test.txt"
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