git multiplayer collaboration

When you clone from a remote repository, Git actually automatically maps the local masterbranch to the remote masterbranch, and the default name of the remote repository is origin.

To view information about a remote library, use git remote:

$ git remote

1. Push branch

To push a branch is to push all local commits on that branch to the remote repository. When pushing, you need to specify the local branch , so that Git will push the branch to the remote branch corresponding to the remote library :

$ git push origin master

If you want to push other branches, for example dev, change it to:

$ git push origin dev

However, it is not necessary to push the local branch to the remote. So, which branches need to be pushed and which ones do not?

masterThe branch is the main branch, so it must be synchronized with the remote at all times ;
devThe branch is the development branch, all members of the team need to work on it, so it also needs to be synchronized with the remote ;
The bug branch is only used to fix bugs locally, there is no need to push it to the remote, unless the boss wants to see how many bugs you fix every week;
Whether the feature branch is pushed to the remote depends on whether you cooperate with your small partners to develop on it.

If your friend wants to develop on the branch dev, he must create a remote branch to the local, so he uses this command to create a local branch:origindevdev

$ git checkout -b dev origin/dev

The push failed because your friend's latest commit conflicts with the commit you're trying to push. The solution is very simple. Git has prompted us to grab git pullthe latest commit first origin/dev, and then merge it locally to resolve the conflict. Push again:

$ git pull

git pullalso failed, because the link of the local devbranch to the remote origin/devbranch was not specified, according to the prompt, set the link of devand origin/dev:

$ git branch --set-upstream dev origin/dev

pull again

$ git pull

This time it git pullwas successful, but there were conflicts in the merge, which needed to be resolved manually. The solution method is exactly the same as the conflict resolution in branch management. After solving, submit, and then push:

$ git commit -m "merge & fix hello.py"
$ git push origin dev

2. Mode

The working mode of multi-person collaboration is usually as follows:

First, you can try to git push origin branch-namepush your own changes;
If the push fails, because the remote branch is newer than your local, you need to git pulltry to merge first;
If the merge has conflicts, resolve the conflicts and commit locally;
If there is no conflict or after the conflict is resolved, git push origin branch-namepush it again and it will be successful!

If it git pullprompts "no tracking information", it means that the link relationship between the local branch and the remote branch has not been created, use the command git branch --set-upstream branch-name origin/branch-name.

Summarize:

View remote library information, use git remote -v;
If the new branch created locally is not pushed to the remote, it will not be visible to others;
Push the branch from the local, use git push origin branch-name, if the push fails, first use to git pullgrab the new remote commit;
Create a branch corresponding to the remote branch locally, use git checkout -b branch-name origin/branch-name, the name of the local and remote branch should be the same;
To establish an association between a local branch and a remote branch, use git branch --set-upstream branch-name origin/branch-name;
从远程抓取分支，使用git pull，如果有冲突，要先处理冲突。

多人协作

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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。

要查看远程库的信息，用git remote：

$ git remote
origin

或者，用git remote -v显示更详细的信息：

$ git remote -v
origin  git@github.com:michaelliao/learngit.git (fetch)
origin  git@github.com:michaelliao/learngit.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。

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！

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:michaelliao/learngit.git
Cloning into 'learngit'...
remote: Counting objects: 46, done.
remote: Compressing objects: 100% (26/26), done.
remote: Total 46 (delta 16), reused 45 (delta 15)
Receiving objects: 100% (46/46), 15.69 KiB | 6 KiB/s, done.
Resolving deltas: 100% (16/16), 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 commit -m "add /usr/bin/env"
[dev 291bea8] add /usr/bin/env
 1 file changed, 1 insertion(+)
$ git push origin dev
Counting objects: 5, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), 349 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
To [email protected]:michaelliao/learngit.git
   fc38031..291bea8  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 hello.py 
$ git commit -m "add coding: utf-8"
[dev bd6ae48] add coding: utf-8
 1 file changed, 1 insertion(+)
$ git push origin dev
To [email protected]:michaelliao/learngit.git
 ! [rejected]        dev -> dev (non-fast-forward)
error: failed to push some refs to '[email protected]:michaelliao/learngit.git'
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Merge the remote changes (e.g. 'git pull')
hint: before pushing again.
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，再推送：

$ git pull
remote: Counting objects: 5, done.
remote: Compressing objects: 100% (2/2), done.
remote: Total 3 (delta 0), reused 3 (delta 0)
Unpacking objects: 100% (3/3), done.
From github.com:michaelliao/learngit
   fc38031..291bea8  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 dev origin/<branch>

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 dev origin/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
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 commit -m "merge & fix hello.py"
[dev adca45d] merge & fix hello.py
$ git push origin dev
Counting objects: 10, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (5/5), done.
Writing objects: 100% (6/6), 747 bytes, done.
Total 6 (delta 0), reused 0 (delta 0)
To [email protected]:michaelliao/learngit.git
   291bea8..adca45d  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，用命令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。