git 之pull的使用

前言
工作中,我们会用到git pull来从远程仓库"同步"代码,通常有三种方式;

git pull origin <remote_branch>:<local_branch>
git pull origin <remote_branch>
git pull

这三种用法充分诠释了什么是简即繁,繁即简;看上去简单的,往往背后蕴藏玄机;

测试环境:
本地分支:master和dev
远程分支:master和dev

$ git branch -a
* dev
  master
  remotes/origin/HEAD -> origin/master
  remotes/origin/dev
  remotes/origin/master

1.git pull origin <remote_branch>:<local_branch>
这种用法写起来最为繁琐,但最好理解:

场景:当本地的当前分支不是local_branch;
作用:将远程分支拉取到指定本地分支;

例如:当前分支是dev,但是你想把远程master”同步”到本地master,但又不想使checkout切换到master分支;
这时你就可以使用git pull origin master:master

zhangchangzhi@ZBXXXX /e/02.Workspace-test/gitTest (dev)
$ git pull origin master:master
From https://github.com/jinxintang/gitTest
   a09fdc4..941758f  master     -> master
Already up-to-date.

从上述代码可以看到,我当前分支为dev,但执行"同步”操作的却是在master分支;

2.git pull origin <remote_branch>
有了上面的例子,这种使用方法的场景和作用就好理解了:

场景:在当前分支上进行同步操作;
作用:将指定远程分支同步到当前本地分支;

废话不说,上代码:

zhangchangzhi@ZBXXX /e/02.Workspace-test/gitTest (dev)
$ git pull origin master
From https://github.com/jinxintang/gitTest
 * branch            master     -> FETCH_HEAD
Already up-to-date.

把远程master分支同步到HEAD分支(HEAD分支指向当前位置);

3.git pull
这种写法最简单,也最常用,但是隐含的知识也是最多的;

场景:本地分支已经和想要拉取的分支建立了“关联”关系;
作用:拉取所有远程分支的新版本"坐标",并同步当前分支的本地代码(具体根据关联分支而定)

什么是"关联"分支?
首先我们先使用git branch -vv 查看一下目前分支的“关联”情况;

$ git branch -vv
* dev    1a1b215 [origin/dev] Merge branch 'master' of https://github.com/jinxintang/gitTest into dev
  master a09fdc4 [origin/master] create pull 

可以看到我们的本地的dev关联的是远程(origin)的dev,本地的master关联的是远程(origin)的master;
那么这种关联是如何建立、是否可以修改呢;
配置本地分支与远程分支的三种方法:
1.检出时建立关联关系:git checkout -b dev origin/dev
当我们检查时,git会自动为我们检出的分支和远程分支建立关联关系;
2.提交时配置关联关系:git push -u origin <remote_branch>或git push --set-upstream origin <remote_branch>

zhangchangzhi@ZB-PF0SB6DQ MINGW64 /e/02.Workspace-test/gitTest (dev_zcz)
$ git branch -vv
* dev_zcz 3b7001a [origin/dev] cm
  master  a09fdc4 [origin/master] create pull

zhangchangzhi@ZB-PF0SB6DQ MINGW64 /e/02.Workspace-test/gitTest (dev_zcz)
$ git push -u origin dev_zcz
Everything up-to-date
Branch dev_zcz set up to track remote branch dev_zcz from origin.

zhangchangzhi@ZB-PF0SB6DQ MINGW64 /e/02.Workspace-test/gitTest (dev_zcz)
$ git branch -vv
* dev_zcz 3b7001a [origin/dev_zcz] cm
  master  a09fdc4 [origin/master] create pull

通过上面的例子可以看到push前dev_zcz关联的是origin/dev,执行push -u 后管理分支改为origin/dev_zcz
注:默认配置下,提交时本地分支需和远程分支同名;

3.更改git/config文件:git branch --set-upstream-to=<remote_branch>

zhangchangzhi@ZB-PF0SB6DQ MINGW64 /e/02.Workspace-test/gitTest (dev_zcz)
$ git branch --set-upstream-to=origin/zcz
Branch dev_zcz set up to track local branch origin/zcz.

zhangchangzhi@ZB-PF0SB6DQ MINGW64 /e/02.Workspace-test/gitTest (dev_zcz)
$ git branch -vv
* dev_zcz    3b7001a [origin/zcz] cm
  master     a09fdc4 [origin/master] create pull
  origin/zcz 3b7001a [dev_zcz] cm

无论使用上述那种方法,本地分支和远程分支的“关联”最终都会写到config文件;

zhangchangzhi@ZB-PF0SB6DQ MINGW64 /e/02.Workspace-test/gitTest/.git (GIT_DIR!)
$ cat config
[core]
        repositoryformatversion = 0
        filemode = false
        bare = false
        logallrefupdates = true
        symlinks = false
        ignorecase = true
[remote "origin"]
        url = https://github.com/jinxintang/gitTest.git
        fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
        remote = origin
        merge = refs/heads/master
[branch "dev_zcz"]
        remote = .
        merge = refs/heads/origin/zcz
[branch "origin/zcz"]
        remote = .
        merge = refs/heads/dev_zcz

注:本项目的配置信息存放目录:项目所在目录/.git/config
看完这三种配置关联分支的方法,想必大家已经对“关联分支”有了一定了解;

关联分支:在git中表现为upstream,无论是使用push -u 或是 git branch --set-upstream-to方法,均会将这种对应关系写入.git/config配置文件,如果一个本地分支没有关联分支,则无法执行 git push 或 git pull指令;

没有"关联"分支的情况下,使用push会先让你设置一个upstream branch.

zhangchangzhi@ZB-PF0SB6DQ MINGW64 /e/02.Workspace-test/gitTest (dev_no_upstream)
$ git branch -vv
* dev_no_upstream 3b7001a cm
  dev_zcz         3b7001a [origin/zcz] cm
  master          a09fdc4 [origin/master] create pull
  origin/zcz      3b7001a [dev_zcz] cm

zhangchangzhi@ZB-PF0SB6DQ MINGW64 /e/02.Workspace-test/gitTest (dev_no_upstream)
$ git push
fatal: The current branch dev_no_upstream has no upstream branch.
To push the current branch and set the remote as upstream, use

    git push --set-upstream origin dev_no_upstream
posted @ 2022-06-05 22:18  xiaoyuanjiangjin  阅读(1896)  评论(0编辑  收藏  举报