Git分支管理（三）

分支如同平行宇宙，如果不合并分支，那么各个分支就互不干扰；如果在某个时间点合并分支，那么合并后的“主分支”就同时拥有了各个分支的内容。其他版本控制系统如SVN等都有分支管理，但是切换分支极慢，但Git的分支，无论创建、切换和删除分支，都能很快完成！

分支在工程开发过程的作用：A和B两人合作开发一个项目；A负责部分需要1个月完成，这期间，如果A一直不提交自己的代码，中途可能代码丢失损失巨大；如果A提交自己的不完善代码，B拿去不完整的代码可能会跑出错误，影响B的开发；这时，如果A创建自己的分支就可以完美解决问题了，A的分支既可以保存A的代码，也可以不让B看到；直到开发完毕后，再一次性合并到原来的分支上，这样，既安全，又不影响别人工作。

在Git里，Git把“每次提交”串成一条时间线，这条时间线就是一个分支。master是主分支，HEAD指针指向的是当前分支。

（1）创建新分支dev，Git新建一个dev指针，指向master相同的提交，再把HEAD指针指向dev分支，就表示当前分支在dev上。【Git创建新分支——增加一个dev指针，将HEAD指针指向dev指针】

（2）在dev分支上的工作完成了，master指针指向dev的当前提交，即完成了把dev分支合并到master上。

（3）删除dev分支，只需要删掉dev指针，有些提交是通过分支完成的！

YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git branch dev   #新建分支dev
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git branch   #查看分支，*指示当前分支
  dev
* master

YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git checkout dev   #切换到dev分支
Switched to branch 'dev'
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git branch
* dev
  master
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ ls
readme.txt	testwrong.txt
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ cat readme.txt 
git maybe better than svn
I just want to try another version management
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ vim readme.txt   #在dev分支下修改文件
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ cat readme.txt 
git maybe better than svn
I just want to try another version management
try branch,just have fun!
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git add readme.txt
 
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git commit -m "branch try"   #在dev分支下更新版本库
[dev 75cf5f2] branch try
 1 file changed, 1 insertion(+)
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git checkout master
Switched to branch 'master'

YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git merge dev   #将dev分支合并到主分支
Updating 981b076..75cf5f2
Fast-forward
 readme.txt | 1 +
 1 file changed, 1 insertion(+)

YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git branch -d dev   #删去dev分支
Deleted branch dev (was 75cf5f2).
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git branch
* master

分支提交修改冲突

YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git checkout -b feature1   #新建并进入分支
Switched to a new branch 'feature1'
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ ls
readme.txt	testwrong.txt
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ cat readme.txt 
git maybe better than svn
I just want to try another version management
try branch,just have fun!
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ vim readme.txt   #在feature1分支下修改文件readme.txt 
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ cat readme.txt 
git maybe better than svn
I just want to try another version management
Creating a new branch is quick AND simple.
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git add readme.txt
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git commit -m "AND simple"
[feature1 da6ba56] AND simple
 1 file changed, 1 insertion(+), 1 deletion(-)

YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git checkout master
Switched to branch 'master'
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ ls
readme.txt	testwrong.txt
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ cat readme.txt 
git maybe better than svn
I just want to try another version management
try branch,just have fun!
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ vim readme.txt   #在主分支下修改文件readme.txt 
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ cat readme.txt 
git maybe better than svn
I just want to try another version management
I try to see branch conflict,just have fun!
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git add readme.txt 
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git commit -m "master change"
[master 6d434eb] master change
 1 file changed, 1 insertion(+), 1 deletion(-)

YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git merge feature1   #合并分支，出现冲突
Auto-merging readme.txt
CONFLICT (content): Merge conflict in readme.txt
Automatic merge failed; fix conflicts and then commit the result.
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git status
On branch master
You have unmerged paths.
  (fix conflicts and run "git commit")
  (use "git merge --abort" to abort the merge)

Unmerged paths:
  (use "git add <file>..." to mark resolution)

	both modified:   readme.txt

no changes added to commit (use "git add" and/or "git commit -a")
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ ls
readme.txt	testwrong.txt
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ cat readme.txt   #查看分支合并冲突文件
git maybe better than svn
I just want to try another version management
<<<<<<< HEAD
I try to see branch conflict,just have fun!
=======
Creating a new branch is quick AND simple.
>>>>>>> feature1
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ vim readme.txt   #手动修改文件，解决冲突 
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ cat readme.txt 
git maybe better than svn
I just want to try another version management
Creating a new branch is quick AND simple.
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git add readme.txt 
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git commit -m "solve conflict by hand"
[master 5cf662f] solve conflict by hand

Fast forward模式：关闭，可记录分支变化历史

合并分支时，如果可能，Git会用Fast forward模式，但这种模式下，删除分支后，会丢掉分支信息。如果要强制禁用Fast forward模式，Git就会在merge时生成一个新的commit，这样，从分支历史上就可以看出分支信息。

YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git checkout -b newbra
Switched to a new branch 'newbra'
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ ls
readme.txt	testwrong.txt
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ cat readme.txt 
git maybe better than svn
I just want to try another version management
Creating a new branch is quick AND simple.
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ vim readme.txt   #修改文件
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ cat readme.txt 
git maybe better than svn
I just want to try another version management
Creating a new branch is quick AND simple.

CHANGE FILE.
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git add readme.txt 
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git commit -m "add merge"
[newbra 576006b] add merge
 1 file changed, 2 insertions(+)
YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git checkout master
Switched to branch 'master'

YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git merge --no-ff -m "merge with no-ff" newbra   #禁用Fast forward模式，可从分支历史上看出分支信息。
Merge made by the 'recursive' strategy.
 readme.txt | 2 ++
 1 file changed, 2 insertions(+)

YYwhdeMacBook-Pro:GITWORKSPACE yywh$ git log --graph --pretty=oneline --abbrev-commit   #查看分支历史变化
*   751edc8 (HEAD -> master) merge with no-ff
|\  
| * 576006b (newbra) add merge
|/  
*   5cf662f solve conflict by hand
|\  
| * da6ba56 (feature1) AND simple
* | 6d434eb master change
|/  
* 75cf5f2 branch try
* 981b076 +wrong example
* c8c2c16 modify readme.txt
* 59dcbd5 + one flie

`git branch：`查看分支

`git branch <name>：`创建分支

`git checkout <name>：`切换分支

`git checkout -b <name>：`创建+切换分支

`git merge <name>：`合并某分支到当前分支

`git branch -d <name>：`删除分支

Git提供了git stash命令，把当前工作现场“储藏”起来，等以后恢复工作现场之后，再继续工作。用git stash list命令，查看刚才的工作现场存到哪。恢复工作现场的办法：（1）用git stash apply恢复工作现场，但是恢复后，stash内容并不删除，你需要用git stash drop来删除；（2）用git stash pop恢复工作现场，恢复的同时把stash内容也删了。此外，可以多次stash，恢复的时候，先用git stash list查看，然后用git stash apply加上指定的stash进行恢复。

通过git branch -D <name>命令，强行删除一个没有被合并过的分支。

从远程仓库克隆时，实际上Git自动把本地的master分支和远程的master分支对应起来，并且，远程仓库的默认名是origin。

（1）git remote，查看远程库的信息；用git remote -v查看更详细的信息：显示fetch和push的origin地址。如果没有推送权限，就看不到push的地址。

（2）git push <far_storage> <local_branch>，把“该分支上的所有本地提交”推送到远程仓库。推送时指定“本地分支”，这样，Git就会把“该分支”推送到远程仓库对应的“远程分支”。

（3）git clone <site>，克隆远程仓库内容。

（4）git checkout -b dev origin/dev，在本地创建和远程origin仓库相同的dev分支。

（5）git branck --set-upstream-to=origin/dev dev，指定本地dev分支与远程origin/dev分支的链接。

（6）git pull，从远程仓库抓取分支，如果有冲突，要先处理冲突。