Re: [PATCH v2 38/43] refs: make some files backend functions public

Michael Haggerty [off-list ref] writes:

quoted

Right now, for cross-backend reads/writes, the lmdb code cheats. It
simply does the write directly and immediately.  This means that these
portions of transactions cannot be rolled back.  That's clearly bad. 

That's a really good point.

I hate to break it to you, but the handling of symrefs in Git is already
a mess. HEAD is the only symref that I would really trust to work
correctly all the time. So I think that changes needn't be judged on
whether they handle symrefs perfectly. They should just not break them
in any dramatic new ways.
...
If everything that I've said is correct, then my opinion is that it
would be perfectly adequate if your code would handle the specific case
of HEAD (by hook or by crook), and if there are any other cross-backend
symrefs, just die with a message stating that such usage is unsupported.
Junio, do you think that would be acceptable?

I find it a very sensible approach.

BTW I just realized that if one backend should delegate to another, then
the primary backend should be the per-worktree backend and it should
delegate to the common backend. I think I described things the other way
around in my earlier message. This makes more sense because it is
acceptable for per-worktree references to refer to common references but
not vice versa.

Sounds good.

Thanks.