Git更新操作

在本文章教程中，我们将演示如何查看 Git 存储库的文件和提交文件记录，并对存储库中的文件作修改和提交。

注意：在开始学习本教程之前，先克隆一个存储库，有关如何克隆存储库，请参考：Git克隆操作

执行克隆操作，并得到了一个新的文件：main.py。想知道谁将这个文件修改变提交到存储库中，那么可以执行git log命令，为了更好的演示，开发人员minsu另外一台机(Ubuntu Linux)上，使用以下命令克隆：

bjpowernode@ubuntu:~$ cd /home/bjpowernode/git
bjpowernode@ubuntu:~/git$ git clone http://git.oschina.net/bjpowernode/sample.git
Cloning into 'sample'...
remote: Counting objects: 15, done.
remote: Compressing objects: 100% (14/14), done.
remote: Total 15 (delta 3), reused 0 (delta 0)
Unpacking objects: 100% (15/15), done.
Checking connectivity... done.
bjpowernode@ubuntu:~/git$

克隆操作将在当前工作目录中创建一个新的目录(sample)。 将目录更改(cd /home/bjpowernode/git/sample)为新创建的目录，并执行git log命令。

bjpowernode@ubuntu:~/git$ cd /home/bjpowernode/git/sample
bjpowernode@ubuntu:~/git/sample$ git log
commit 51de0f02eb48ed6b84a732512f230028d866b1ea
Author: your_name 
Date:   Fri Jul 7 23:04:16 2017 +0800

    add the sum of a & b

commit be24e214620fa072efa877e1967571731c465884
Author: your_name 
Date:   Fri Jul 7 18:58:16 2017 +0800

    ？？mark

commit 5eccf92e28eae94ec5fce7c687f6f92bf32a6a8d
Author: your_name 
Date:   Fri Jul 7 18:52:06 2017 +0800

    this is main.py file commit mark use -m option

commit 6e5f31067466795c522b01692871f202c26ff948
Author: your_name 
Date:   Fri Jul 7 18:42:43 2017 +0800

    this is main.py file commit mark without use "-m" option

commit 290342c270bc90f861ccc3d83afa920169e3b07e
Author: Maxsu <769728683@qq.com>
Date:   Fri Jul 7 16:55:12 2017 +0800

    Initial commit
bjpowernode@ubuntu:~/git/sample$

观察日志后，可以看到maxsu添加了文件代码来实现两个变量a和b之和，现在假设minsu在文本编辑器中打开main.py，并修改优化代码。在示两个变量a和b之和，定义一个函数来实现两个变量之和。修改后，代码如下所示：

#!/usr/bin/python3
#coding=utf-8

a = 10
b = 20

def sum(a, b):
    return (a+b)

c = sum(a, b)
print("The value of c is  ", c)

使用 git diff 命令查看更改，如下所示：

bjpowernode@ubuntu:~/git/sample$ git diff
diff --git a/main.py b/main.py
index 25eb22b..e84460d 100644
--- a/main.py
+++ b/main.py
@@ -7,5 +7,9 @@ print ("Life is short, you need Python !")
 a = 10

 b = 20
-c = a + b
-print("The value of c is  ", c)
\ No newline at end of file
+
+def sum(a, b):
+    return (a+b)
+
+c = sum(a, b)
+print("The value of c is  ", c)
bjpowernode@ubuntu:~/git/sample$

经过测试，代码没有问题，提交了上面的更改。

bjpowernode@ubuntu:~/git/sample$ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes not staged for commit:
  (use "git add ..." to update what will be committed)
  (use "git checkout -- ..." to discard changes in working directory)

        modified:   main.py

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

bjpowernode@ubuntu:~/git/sample$ git add main.py
bjpowernode@ubuntu:~/git/sample$ git commit -m "add a new function sum(a,b)"
[master 01c5462] add a new function sum(a,b)
 1 file changed, 6 insertions(+), 2 deletions(-)
bjpowernode@ubuntu:~/git/sample$

再次查看提交记录信息：

bjpowernode@ubuntu:~/git/sample$ git log
commit 01c54624879782e4657dd6c166ce8818f19e8251
Author: minsu 
Date:   Sun Jul 9 19:01:00 2017 -0700

    add a new function sum(a,b)

commit 51de0f02eb48ed6b84a732512f230028d866b1ea
Author: your_name 
Date:   Fri Jul 7 23:04:16 2017 +0800

    add the sum of a & b
....

经过上面添加和提交修改后，其它开发人员并不能看到代码中定义的 sum(a, b) 函数，还需要将这里提交的本地代码推送到远程存储库。使用以下命令：

bjpowernode@ubuntu:~/git/sample$ git push origin master
Username for 'http://git.oschina.net': 769728683@qq.com
Password for 'http://769728683@qq.com@git.oschina.net':<你的帐号的密码>
Counting objects: 3, done.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 419 bytes | 0 bytes/s, done.
Total 3 (delta 0), reused 0 (delta 0)
To http://git.oschina.net/bjpowernode/sample.git
   51de0f0..01c5462  master -> master
bjpowernode@ubuntu:~/git/sample$

现在，代码已经成功提交到远程存储库中了，只要其它开发人员使用 git clone 或 git pull 就可以得到这些新提交的代码了。

下面我们将学习其它一些更为常用的 git 命令，经过下面的学习，你就可以使用这些基本的git操作命令来文件和代码管理和协同开发了。

添加新函数

在开发人员B(minsu)修改文件main.py中的代码的同时，开发人员A(maxsu)在文件main.py中实现两个变量的乘积函数。 修改后，main.py文件如下所示：

#!/usr/bin/python3
#coding=utf-8

print ("Life is short, you need Python !")


a = 10

b = 20
c = a + b
print("The value of c is  ", c)

def mul(a, b):
    return (a * b)

现在修改完代码，运行以下命令：

$ git diff

得到如下结果：

现在添加并提交上面的代码：

$ git status
On branch master
Your branch is up-to-date with 'origin/master'.

Changes not staged for commit:
  (use "git add ..." to update what will be committed)
  (use "git checkout -- ..." to discard changes in working directory)

        modified:   main.py

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

$ git add main.py

Administrator@MY-PC /D/worksp/sample (master)
$ git commit -m "add a mul(a, b) function"
[master e5f8dfa] add a mul(a, b) function
 1 file changed, 4 insertions(+), 1 deletion(-)

现在查看上提交的日志信息，如下结果：

$ git log
commit e5f8dfa9e7e89fea8813ab107e14b9b7412df2ae
Author: your_name 
Date:   Sun Jul 9 23:06:32 2017 +0800

    add a mul(a, b) function

commit 51de0f02eb48ed6b84a732512f230028d866b1ea
Author: your_name 
Date:   Fri Jul 7 23:04:16 2017 +0800

    add the sum of a & b
... ...

好了，现在要将上面的代码推送到远程存储库，使用以下命令：

$ git push origin master

执行上面命令，结果如下：

$ git push origin master
Username for 'http://git.oschina.net': 769728683@qq.com
Password for 'http://769728683@qq.com@git.oschina.net':
To http://git.oschina.net/bjpowernode/sample.git
 ! [rejected]        master -> master (fetch first)
error: failed to push some refs to 'http://git.oschina.net/bjpowernode/sample.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

但Git推送失败。因为Git确定远程存储库和本地存储库不同步。为什么呢?因为在向文件main.py添加以下代码片段时：

def mul(a, b):
    return (a * b)

另外一个开发人员B已经向远程存储库推送修改的代码，所以这里在向远程存储库推送代码时，发现上面的新的推送代码，现在这个要推送的代码与远程存储库中的代码不一致，如果强行推送上去，Git不知道应该以谁的为准了。

所以，必须先更新本地存储库，只有在经过此步骤之后，才能推送自己的改变。

获取最新更改

执行git pull命令以将其本地存储库与远程存储库同步。

$ git pull
remote: Counting objects: 3, done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
From http://git.oschina.net/bjpowernode/sample
   51de0f0..01c5462  master     -> origin/master
Auto-merging main.py
CONFLICT (content): Merge conflict in main.py
Automatic merge failed; fix conflicts and then commit the result.

现在打开 main.py 内容如下：

#!/usr/bin/python3
#coding=utf-8

print ("Life is short, you need Python !")


a = 10

b = 20
<<<<<<< HEAD
c = a + b
print("The value of c is  ", c)

def mul(a, b):
    return (a * b)
=======

def sum(a, b):
    return (a+b)

c = sum(a, b)
print("The value of c is  ", c)
>>>>>>> 01c54624879782e4657dd6c166ce8818f19e8251

拉取操作后，检查日志消息，并发现其它开发人员的提交的详细信息，提交ID为：01c54624879782e4657dd6c166ce8818f19e8251

打开 main.py 文件，修改其中的代码，修改完成后保文件，文件的代码如下所示：

#!/usr/bin/python3
#coding=utf-8

print ("Life is short, you need Python !")

a = 10
b = 20

c = a + b
print("The value of c is  ", c)

def mul(a, b):
    return (a * b)

def sum(a, b):
    return (a+b)

c = sum(a, b)
print("The value of c is  ", c)

再次添加提交，最后推送，如下命令：

$ git add main.py

Administrator@MY-PC /D/worksp/sample (master|MERGING)
$ git commit -m "synchronized with the remote repository "
[master ef07ab5] synchronized with the remote repository

Administrator@MY-PC /D/worksp/sample (master)
$ git status
On branch master
Your branch is ahead of 'origin/master' by 2 commits.
  (use "git push" to publish your local commits)

nothing to commit, working directory clean

Administrator@MY-PC /D/worksp/sample (master)
$ git push origin master
Username for 'http://git.oschina.net': 769728683@qq.com
Password for 'http://769728683@qq.com@git.oschina.net':
Counting objects: 10, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (6/6), done.
Writing objects: 100% (6/6), 657 bytes | 0 bytes/s, done.
Total 6 (delta 2), reused 0 (delta 0)
To http://git.oschina.net/bjpowernode/sample.git
   01c5462..ef07ab5  master -> master

现在，一个新的代码又提交并推送到远程存储库中了。