git fetch vs. git fetch origin master对跟踪分支有不同的影响 [英] git fetch vs. git fetch origin master have different effects on tracking branch

问题描述

这主要是好奇心的本质，因为我试图熟悉Git。我已经看过'git fetch'的文档，但是我没有看到下面的明显解释。 1）从一个中央仓库中，比如说GitHub，我克隆一个名为的仓库，网站名为。 / code>在两台机器上， HostA 和 HostB 。
$ b 2）在 HostA 上，我修改了一个文件，比如 README。 txt ，并提交它。

此时在 HostA 上，提交分支 master 和
origin / master 与预期不同，因为我还没有推出

  git show master 
 git show origin / master 
  

报告不同的散列值（因为 master 有变化， origin / master 不会）

3）一旦我推，他们在那之后也是这样。

---

4）现在，在 HostB 上，如果我做了以下操作：

  git fetch 
 git merge FETCH_HEAD 
  

之后，在HostB 当使用 git show 和 origin / master 报告相同的散列>

但是



如果我在 HostB

  git fetch origin master 
 git merge FETCH_HEAD 
  

  git show origin 
 git show origin / master 
 
 / code> 

报告不同的哈希值

跟踪分支 origin / master 不会更新，直到我做了一个普通的 git fetch

这是为什么？

解决方案

如果您的分支有关联远程跟踪分支，这意味着它的配置如下所示：

  git config branch。[branch-name] .remote [remote-name] 
 git config branch。[branch-name] .merge [remote-master] 
  

的关键部分 git fetch 这两个命令的区别在于：

 < refspec> 
  

< refspec> 参数是一个可选的 + ，然后是源代码< src> ，后跟一个冒号：，后跟目的地ref < dst> 。

获取匹配< src> 的远程ref，如果< dst> 不是空字符串，则 ，使用< src> 。

快速转发与之匹配的本地裁判

让我再说一遍：

如果< dst> 不是空字符串，与之匹配的本地引用使用< src> 快速转发。

知道：

• git fetch 相当于 git fetch origin master：master （来自分支配置的默认值），所以它会更新远程跟踪麸皮ch： refspec的目的地是为您指定的。

  
  

• git fetch origin master 相当于 git fetch origin master：，而不是 git fetch origin master：master ;它在 FETCH_HEAD中存储' master '分支（远程' origin '）的获取值，而不在' master '分支或远程追踪'远程/原产地/主人'分支（来自 JakubNarębski的你没有指定你的refspec的目的地

This is mostly of the nature of a curiosity as I'm trying to get familiar with Git. I have looked at the documentation for 'git fetch' but I don't see an obvious explanation for the below. Thanks in advance, and apologies if this is howlingly obvious.

1) From a central repository, say GitHub, I clone a repository named website on each of two machines, HostA and HostB.

2) on HostA, I make a change to a file, say README.txt, and commit it.
At this point on HostA, the commits for branches master and origin/master are, as expected different since I haven't pushed yet

git show master
git show origin/master

report different hashes (since master has the change and origin/master does not)

3) Once I push, they are after that the same.

---

4) Now, over on HostB, if I do the following:

git fetch
git merge FETCH_HEAD

afterwards, on HostB master and origin/master report the same hash when queried with git show

BUT

if instead I had done, on HostB:

git fetch origin master
git merge FETCH_HEAD

at that point the hashes still differ.

git show origin
git show origin/master

report different hashes

The tracking branch origin/master isn't updated until I do a plain git fetch

Why is this?

解决方案

If your branch has an associated remote tracking branch that means its configuration is like:

git config branch.[branch-name].remote [remote-name]
git config branch.[branch-name].merge [remote-master]

The key part of git fetch which explain the difference between the two commands is:

<refspec>

The format of a <refspec> parameter is an optional plus +, followed by the source ref <src>, followed by a colon :, followed by the destination ref <dst>.
The remote ref that matches <src> is fetched, and if <dst> is not empty string, the local ref that matches it is fast-forwarded using <src>.

Let me repeat it:

if <dst> is not empty string, the local ref that matches it is fast-forwarded using <src>.
Knowing that:

• git fetch is equivalent to git fetch origin master:master (from the default value of your branch config), so it will update the remote tracking branch: the destination of the refspec is specified for you.

• git fetch origin master is equivalent to "git fetch origin master:", not to "git fetch origin master:master"; it stores fetched value of 'master' branch (of remote 'origin') in FETCH_HEAD, and not in 'master' branch or remote-tracking 'remotes/origin/master' branch (from Jakub Narębski's answer)
  In other words, you didn't specify the destination of your refspec

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