为什么我需要 git merge origin/master 中的“master”？

使用 git 并且您希望从服务器获取更改时的约定是：

git fetch

git merge origin/master

我知道还有git pull，但我的具体问题是关于语法的origin/master。什么是master部分做什么？如果我只是这样做git merge origin（没有master）似乎有效。我知道master是一个分支，但如果我正在跟踪远程的多个分支，正常用例是否会合并所有分支？

论据merge已解析为提交 ID。这意味着规则中git 修订版被应用。一般来说，origin/name解析为“远程分支”之一git fetch and git push保持每次获取和推送的最新状态。

“远程分支”，也称为“远程跟踪分支”，只是一个类似分支的标签，其“全名”以refs/remotes/。远程名称的所有名称origin are in refs/remotes/origin/。正常运行时git fetch咨询一些远程（例如origin) git 存储库并询问它：“嘿，你那里有哪些分支，它们的 SHA-1 值是多少？”当它得到答案时，它将它们存储在本地yourgit 存储库：refs/remotes/origin/master, refs/remotes/origin/devel， 等等。这样你就可以知道你的 git 上次有机会同步时“那边”的情况是什么样的。

这些不应与 git 所谓的“跟踪分支”（或“本地跟踪分支”）混淆。本地分支机构是“全名”开头的标签refs/heads/。如果它们具有与其相关的“上游”信息，则它们被视为“跟踪”。您可以在第一次创建分支时放入上游信息 - 这通常是与远程分支具有“相同”名称的本地分支的情况，例如master vs origin/master—或者您可以稍后设置（或更改）它git branch --set-upstream-to.

All of these are different from the git pull syntax: git pull origin master is rather different, and much older, predating the whole idea of "remote-tracking branches" entirely.¹ This sort of accidental resemblance, as it were, I think is the source of a whole lot of confusion (I know I found it confusing, years ago).

¹Specifically, you used to (and still can) git pull from a URL rather than a "remote" name. That went (and still goes) over to the other git repository as usual, and gets a list of at least some of its branches (sometimes just the one of interest). But, because those are its branches, not yours, they are then recorded in a file called FETCH_HEAD. So at this point, it will have brought master over from "over there", but put it into FETCH_HEAD rather than a remote-tracking branch—with a raw URL, you don't have a remote name, so there's no way to name the remote-tracking branch: there's no origin with which to construct the prefix refs/remotes/origin. The master argument to git-pull then means: "go search through FETCH_HEAD to find their master branch."