What is HEAD in Git?

Question

You see the Git documentation saying things like

The branch must be fully merged in HEAD.

But what is Git HEAD exac

Answer 1

I am also still figuring out the internals of git, and have figured out this so far:

Let's say the current branch is master.

1. HEAD is a file in your .git/ directory that normally looks something like this:

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

2. refs/heads/master is itself a file that normally has the hash value of the latest commit of master:

% cat .git/refs/heads/master 
f342e66eb1158247a98d74152a1b91543ece31b4

3. If you do a git log, you will see that this is the latest commit for master:

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

So my thinking is the HEAD file is a convenient way to track the latest commit, instead of remembering long hash values.