If I run git checkout --orphan my_new_branch, then .git/HEAD points to a ref that does not (yet) exist.

git checkout --orphan my_new_branch
Switched to a new branch 'my_new_branch'

cat .git/HEAD
ref: refs/heads/my_new_branch

git show-ref refs/heads/my_new_branch
# No output

ls .git/refs/heads/my_new_branch
ls: cannot access '.git/refs/heads/my_new_branch': No such file or directory

Mostly out of curiosity, I tried to replicate this state using update-ref and symbolic-ref, but git seems to disallow this:

git update-ref  HEAD 'refs/heads/my_new_branch'
fatal: refs/heads/my_new_branch: not a valid SHA1

git symbolic-ref HEAD 'ref: refs/heads/my_new_branch'
fatal: Refusing to point HEAD outside of refs/

Is there some other plumbing command invocation that can explicitly move HEAD to point at a non-existent ref, without all the other side effects of git checkout --orphan?

I am aware that I can just do echo "ref: refs/heads/my_new_branch" > .git/HEAD, but I am curious to learn about whether directly writing to the file is the only approach.

Output of git -v, in case the behavior is version-dependent:

git version 2.47.0