On Tue, Aug 19, 2025 at 10:05:19AM +0200, Patrick Steinhardt wrote:

quoted

I didn't include a test here because it requires corrupting the
repository in a way that is only easy to do using the files ref backend.
It doesn't seem worth carrying a REFFILES test just for this oddity.

True:

    $ git update-ref HEAD HEAD^{tree}
    fatal: update_ref failed for ref 'HEAD': trying to write non-commit object 4b825dc642cb6eb9a060e54bf8d69288fbee4904 to branch 'HEAD'

But:

    $ git update-ref refs/some/tree HEAD^{tree}
    $ git symbolic-ref HEAD refs/some/tree
    $ git show
    tree HEAD

So that should allow you to write a test, right?

Hrm, that seems like a bug. I thought we insisted that HEAD point at
refs/heads.

Ah, no. We did that in b229d18a80 (validate_headref: tighten
ref-matching to just branches, 2009-01-29), but had to revert it in
e9cc02f0e4 (symbolic-ref: allow refs/<whatever> in HEAD, 2009-02-13) to
keep compatibility for topgit. :(

Still, I'm not sure it's something I'd want to base a test on. Maybe if
there is a big comment that says "It is OK to invalidate and remove this
test if we ever tighten symbolic-ref" it would be OK?

-Peff