Re: [PATCH 1/1] worktree refs: fix case sensitivity for 'head'

On Fri, Dec 14, 2018 at 9:38 AM Duy Nguyen [off-list ref] wrote:

On Fri, Dec 14, 2018 at 6:22 PM Jacob Keller [off-list ref] wrote:

quoted

On Thu, Dec 13, 2018 at 11:38 PM Duy Nguyen [off-list ref] wrote:

quoted

Even with a new ref storage, I'm pretty sure pseudo refs like HEAD,
FETCH_HEAD... will forever be backed by filesystem. HEAD for example
is part of the repository signature and must exist as a file. We could
also lookup pseudo refs with readdir() instead of lstat(). On
case-preserving-and-insensitive filesystems, we can reject "head" this
way. But that comes with a high cost.
--
Duy

Once other refs are backed by something that doesn't depend on
filesystem case sensitivity, you could enforce that we only accept
call-caps HEAD as a psuedo ref, and always look up other spellings in
the other refs backend, though, right?

Hmm.. yes. I don't know off hand if we have any pseudo refs in
lowercase. Unlikely so yes this should work.

I think even if we had lowercase pseudo refs, as long as we know which
identifiers represent pseudo refs, and we don't have two variants
which match if compared case insensitively, we shouldn't have
ambiguity, since we'd distinguish whether to check a pseudo ref spot
before we actually check the file system.

quoted

So, yea the actual file may not
be case sensitive, but we would never create refs/head anymore for any
reason, so there would be no ambiguity if reading the refs/head vs
refs/HEAD on a case insensitive file system, since refs/head would no
longer be a legitimate ref stored as a file if you used a different
refs backend.

Basically, we'd be looking up HEAD by checking the file, but we'd stop
looking up head, hEAd, etc in the files, and instead use whatever
other refs backend for non-pseudo refs. Thus, it wouldn't matter,
since we'd never actually lookup the other spellings of HEAD as a
file. Wouldn't that solve the ambiguity, at least once a repository
has fully switched to some alternative refs backend for non-pseudo
refs? (Unless I mis-understand and refs/head could be an added pseudo
ref?)

No I think "pseudo refs" are those outside "refs" directory only. So
"refs/head" would be a "normal" ref.

Right, I was a bit confused pre-coffee and forgot why a ref was a pseudo ref.

quoted

Jake

--
Duy