Re: [PATCH v3 2/4] remote: use remote_state parameter internally

Junio C Hamano [off-list ref] writes:

quoted

c) Replace the backpointer with a remote_state parameter. Expressive and
   fits the paradigm of "defaulting to the repo when needed", but
   interfaces are repetitive and shifts the responsibility of
   correctness to the caller (see v2).

... if we want to support the what-if callers, I
think the best approach would be a slight variant of c) above.

That is, pass branch and remote_state as two parameters, and when
branch is not NULL, barf if it is not among remote_state.branches[],
to protect against nonsense combinations.

Sounds reasonable to me. The resulting interface would look like the v2
one, but internally, this additional safety check will prevent misuse.

quoted

quoted

a) Represent detached HEAD with a non-NULL "struct branch". This will
   let us continue using the remote_state backpointer, which makes many
   interfaces clean, but is somewhat invasive, error-prone and it uses
   "struct branch" for something that is not a branch, which is itself
   an error-prone interface.

I'd rather not to go there.

Actually, I take half of that back, as I think this would be the
best direction in the longer term, and it conceptually is sound.
After all, detached HEAD is not all that special--- when we ask for
the "current branch" and the HEAD happens to be detached, we treat
it as a perfectly valid state and behave as if we are on that
unnamed branch.  The state probably deserves to be represented as a
"struct branch" instance.
[...] when things have stabilized, we should revisit
and see if it is feasible to represent a detached HEAD state with an
instance of "struct branch" and how simpler the interface would become
when we did so.

This "longer term direction" sounds like what I envisioned with (e). I
agree that detached HEAD is a state that should be expressed with more
than just NULL, though I'm not sure that "struct branch" is the correct
abstraction. No point bikeshedding now of course, we'll cross that
bridge when we get there ;)