HEAD只是一个特殊的指针，它指向您当前所在的本地分支。

从Pro Git书籍3.1章Git分支-果壳中的分支，在部分创建一个新的分支:

What happens if you create a new branch? Well, doing so creates a new pointer for you to move around. Let’s say you create a new branch called testing. You do this with the git branch command: $ git branch testing This creates a new pointer at the same commit you’re currently on How does Git know what branch you’re currently on? It keeps a special pointer called HEAD. Note that this is a lot different than the concept of HEAD in other VCSs you may be used to, such as Subversion or CVS. In Git, this is a pointer to the local branch you’re currently on. In this case, you’re still on master. The git branch command only created a new branch — it didn’t switch to that branch.

HEAD只是一个特殊的指针，它指向您当前所在的本地分支。

从Pro Git书籍3.1章Git分支-果壳中的分支，在部分创建一个新的分支:

What happens if you create a new branch? Well, doing so creates a new pointer for you to move around. Let’s say you create a new branch called testing. You do this with the git branch command: $ git branch testing This creates a new pointer at the same commit you’re currently on How does Git know what branch you’re currently on? It keeps a special pointer called HEAD. Note that this is a lot different than the concept of HEAD in other VCSs you may be used to, such as Subversion or CVS. In Git, this is a pointer to the local branch you’re currently on. In this case, you’re still on master. The git branch command only created a new branch — it didn’t switch to that branch.

您可以将HEAD视为“当前分支”。当您使用git签出切换分支时，HEAD修订将更改为指向新分支的尖端。

你可以通过这样做来查看HEAD指向什么:

cat .git/HEAD

在我的例子中，输出是:

$ cat .git/HEAD
ref: refs/heads/master

HEAD可以引用与分支名称不关联的特定修订。这种情况被称为分离HEAD。

我还在弄清楚git的内部结构，到目前为止，我已经弄清楚了这个:

假设当前的分支是master。

HEAD是你的.git/目录下的一个文件，通常看起来像这样:

% cat .git/HEAD
ref: refs/heads/master

Refs /heads/master本身是一个文件，通常包含master最新提交的哈希值:

% cat .git/refs/heads/master 
f342e66eb1158247a98d74152a1b91543ece31b4

如果你做git日志，你会看到这是master的最新提交:

% git log --oneline 
f342e66 (HEAD -> master,...) latest commit
fa99692 parent of latest commit

所以我的想法是HEAD文件是一种跟踪最新提交的方便方法，而不是记住长散列值。

Git都是关于提交的。 Head指向当前签出的提交。

$ git cat-file -t HEAD
commit

无论何时签出一个分支，HEAD都指向该分支上的最新提交。HEAD的内容可检查如下(主分支):

$ cat .git/refs/heads/master
  b089141cc8a7d89d606b2f7c15bfdc48640a8e25

假设这不是一种叫做“分离HEAD”的特殊情况，那么，正如O'Reilly Git书第2版第69页所述，HEAD的意思是:

HEAD总是指当前节点上最近的提交 分支。当您更改分支时，HEAD将被更新为引用新的分支 布兰奇的最新提交。

so

HEAD是当前分支的“尖端”。

注意，我们可以使用HEAD表示最近的提交，使用HEAD~表示提示之前的提交，使用HEAD~~或HEAD~2表示更早的提交，以此类推。