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 usrbin/env"

    [dev 291bea8] add usrbin/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 git@github.com:michaelliao/learngit.git

    fc38031..291bea8 dev -> dev

    http://michaelliao.gitcafe.io/video/git-push-by-xiaohuoban.mp4

    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 git@github.com:michaelliao/learngit.git

    ! [rejected] dev -> dev (non-fast-forward)

    error: failed to push some refs to 'git@github.com: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 git@github.com:michaelliao/learngit.git

    291bea8..adca45d dev -> dev

    http://michaelliao.gitcafe.io/video/git-pull-push-fix.mp4

    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。