this post was submitted on 08 Mar 2024
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How HEAD works in git (jvns.ca)
submitted 8 months ago by canpolat to c/git
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[–] Kissaki 2 points 8 months ago (1 children)

Detached HEAD meaning that the HEAD ref doesn’t point to the same commit as the branch ref that always follows the last commit in a development branch

IMO this is misleading, or incomplete.

HEAD is different from branches in that it can point to a commit or a branch. A branch always points to a commit.

When HEAD is in [branch] detached state, there is no branch to refer to/we can refer to. We are outside of branches.

From a use case perspective that may illustrate the difference:

When HEAD points to a branch, and I commit, I commit to that branch.

When HEAD points to a commit ([branch] detached HEAD), and I commit, I create a commit, and HEAD points to the new commit, but there is no branch pointing to it. (A followup is needed, e.g. creating a branch, or updating an existing branch, to keep the new commit discoverable even after we change what HEAD points to - e.g. by switching to a branch.)

I thought HEAD was just a ref

"refs" are stored in .git/refs/heads - but HEAD is not. In that sense, HEAD is not a ref like the others (branches and tags and whatever else you put there, like pull request references).

HEAD is either a reference or a reference to a reference. Branches are references.

[–] [email protected] 3 points 8 months ago

HEAD is different from branches in that it can point to a commit or a branch. A branch always points to a commit.

That's what I was saying.

When HEAD is in [branch] detached state, there is no branch to refer to/we can refer to. We are outside of branches.

You can still be in detached HEAD state and still be in a branch in a sense that your working tree reflects a commit that's in a series of commit that follow a certain bifurcation. If that makes any sense.

But as soon as you make changes and commit, you create a "branch within a branch" though that "branch" doesn't have a branch ref pointing to it.