[jameshart]

A branch is not a ref.

A head ref is a ref that names a branch. But branches can exist in git without refs. Branches are artifacts that exist in the commit DAG - they are dangling chains of commits that end without being merged in to some other commit. They exist, as pure platonic branches, even if they are un-referenced.

But then you can make a head ref and name one and now all of a sudden you have a named branch. As you make more commits that extend the branch while ‘attached’ to that head, the head ref follows the tip of the branch (that is in particular a thing a head ref does that a tag ref does not).

But you can add commits and extend a branch in a detached state of you like - no head refs following the branch tip. Yet the branch definitely exists. And then if you tag it, you name it.

So no, I don’t think “a branch is a ref” tells the whole story.

[rmwaite]

This is a strange take, in my opinion. Dangling commits like those you describe will be cleaned up by the the garbage collector. To say that a “branch” exists without a branch ref pointing to it is at best purely pedantic. Without a ref there is no meaningful branch because it will disappear eventually.