12.GIT多人协作

当你从远程仓库克隆时,实际上Git自动把本地的master分支和远程的master分支对应起来了,并且,远程仓库的默认名称是origin.

查看远程库的信息
$ git remote
origin

$ git remote -v
origin  https://github.com/apollo1616/test.git (fetch)
origin  https://github.com/apollo1616/test.git (push)
# 上面显示了可以抓取和推送的origin的地址.如果没有推送权限,就看不到push的地址.

1 推送分支

推送分支,就是把该分支上的所有本地提交推送到远程库.推送时,要指定本地分支,这样,Git就会把该分支推送到远程库对应的远程分支上:
$ git push origin master

如果要推送其他分支,比如dev,就改成:
$ git push origin dev

但是,并不是一定要把本地分支往远程推送,那么,哪些分支需要推送,哪些不需要呢？
master分支是主分支,因此要时刻与远程同步;
dev分支是开发分支,团队所有成员都需要在上面工作,所以也需要与远程同步;
bug分支只用于在本地修复bug,就没必要推到远程了,除非老板要看看你每周到底修复了几个bug;
feature分支是否推到远程,取决于你是否和你的小伙伴合作在上面开发.
总之,就是在Git中,分支完全可以在本地自己藏着玩,是否推送,视你的心情而定!

2 抓取分支

多人协作时,大家都会往master和dev分支上推送各自的修改.
现在,模拟一个你的小伙伴,可以在另一台电脑(注意要把SSH Key添加到GitHub)或者同一台电脑的另一个目录下克隆：

$ git clone git@github.com:triaquae/gitskills.git
Cloning into 'gitskills'...
remote: Counting objects: 16, done.
remote: Compressing objects: 100% (7/7), done.
remote: Total 16 (delta 0), reused 10 (delta 0), pack-reused 0
Receiving objects: 100% (16/16), done.
Checking connectivity... done.

当你的小伙伴从远程库clone时，默认情况下，你的小伙伴只能看到本地的master分支。不信可以用git branch命令看看：
$ git branch
* master

现在，你的小伙伴要在dev分支上开发，就必须创建远程origin的dev分支到本地，于是他用这个命令创建本地dev分支：
$ git checkout -b dev origin/dev

现在，他就可以在dev上继续修改，然后，时不时地把dev分支push到远程：
$ git add .
$ git commit -m "small updates"

[dev f1b762e] small updates
 2 files changed, 5 insertions(+), 1 deletion(-)
Alexs-MacBook-Pro:gitskills alex$ git push origin dev
Counting objects: 4, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (4/4), 438 bytes | 0 bytes/s, done.
Total 4 (delta 0), reused 0 (delta 0)
To git@github.com:triaquae/gitskills.git
   33ec6b4..f1b762e  dev -> dev

你的小伙伴已经向origin/dev分支推送了他的提交，而碰巧你也对同样的文件作了修改，并试图推送:
$ git add .
$ git commit -m "add Dog class"
[dev 7e7b1bf] add Dog class
 2 files changed, 7 insertions(+)

$ git push origin dev

To git@github.com:triaquae/gitskills.git
 ! [rejected]        dev -> dev (fetch first)
error: failed to push some refs to 'git@github.com:triaquae/gitskills.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. #提示你了，先把远程最新的拉下来再提交你的
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

推送失败，因为你的小伙伴的最新提交和你试图推送的提交有冲突，解决办法也很简单，Git已经提示我们，先用git pull把最新的提交从origin/dev抓下来，然后，在本地合并，解决冲突，再推
$ git pull
remote: Counting objects: 4, done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 4 (delta 0), reused 4 (delta 0), pack-reused 0
Unpacking objects: 100% (4/4), done.
From github.com:triaquae/gitskills
   33ec6b4..f1b762e  dev        -> origin/dev
There is no tracking information for the current branch.
Please specify which branch you want to merge with.
See git-pull(1) for details.

    git pull <remote> <branch>

If you wish to set tracking information for this branch you can do so with:

    git branch --set-upstream-to=origin/<branch> dev

git pull也失败了，原因是没有指定本地dev分支与远程origin/dev分支的链接，根据提示，设置dev和origin/dev的链接：
$ git branch --set-upstream-to=origin/dev dev
Branch dev set up to track remote branch dev from origin.

再pull：
$ git pull
Auto-merging hello.py
CONFLICT (content): Merge conflict in hello.py
Auto-merging branch_test.md
CONFLICT (content): Merge conflict in branch_test.md
Automatic merge failed; fix conflicts and then commit the result.

这回git pull成功，但是合并有冲突，需要手动解决，解决的方法和分支管理中的解决冲突完全一样。解决后，提交，再push：　　
$ git add .
$ git commit -m "merge & fix hello.py"
[dev 93e28e3] merge & fix hello.py

$ git push origin dev

Counting objects: 8, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (7/7), done.
Writing objects: 100% (8/8), 819 bytes | 0 bytes/s, done.
Total 8 (delta 1), reused 0 (delta 0)
remote: Resolving deltas: 100% (1/1), done.
To git@github.com:triaquae/gitskills.git
   f1b762e..93e28e3  dev -> dev

因此,多人协作的工作模式通常是这样:
首先,可以试图用git push origin branch-name推送自己的修改;
	如果推送失败,则因为远程分支比你的本地更新,需要先用git pull试图合并;
	如果合并有冲突,则解决冲突,并在本地提交;
    没有冲突或者解决掉冲突后,再用git push origin branch-name推送就能成功!
如果git pull提示“no tracking information”,则说明本地分支和远程分支的链接关系没有创建.
	执行命令: git branch --set-upstream branch-name origin/branch-name。
这就是多人协作的工作模式,一旦熟悉了,就非常简单.