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From: Duy Nguyen <pclouds@gmail.com>
To: Jacob Keller <jacob.keller@gmail.com>
Cc: Mike Rappazzo <rappazzo@gmail.com>,
	Stefan Beller <sbeller@google.com>,
	gitgitgadget@gmail.com, Git Mailing List <git@vger.kernel.org>,
	Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH 1/1] worktree refs: fix case sensitivity for 'head'
Date: Fri, 14 Dec 2018 08:37:41 +0100	[thread overview]
Message-ID: <CACsJy8D9qfBLOUCyca+ws66uHx_tgoFZSTbTBxxW2fRQmyr_Nw@mail.gmail.com> (raw)
In-Reply-To: <CA+P7+xonxvfuhw4W+FUL87We8CaOwxsndFkN5bcgBhdsnZ5QAg@mail.gmail.com>

On Fri, Dec 14, 2018 at 7:50 AM Jacob Keller <jacob.keller@gmail.com> wrote:
>
> On Thu, Dec 13, 2018 at 1:16 PM Mike Rappazzo <rappazzo@gmail.com> wrote:
> >
> > On Thu, Dec 13, 2018 at 3:48 PM Stefan Beller <sbeller@google.com> wrote:
> > >
> > > > > The current situation is definitely a problem.  If I am in a worktree,
> > > > > using "head" should be the same as "HEAD".
> > >
> > > By any chance, is your file system case insensitive?
> > > That is usually the source of confusion for these discussions.
> >
> > This behavior is the same for MacOS (High Sierra) and Windows 7.  I
> > assume other derivatives of those act the same.
> >
> > On CentOS "head" is an ambiguous ref.  If Windows and Mac resulted in
> > an ambiguous ref, that would also be OK, but as it is now, they return
> > the result of "HEAD" on the primary worktree.
> >
>
> Because refs are *not* case sensitive, and we know that "HEAD" should
> be per-worktree, it gets checked in the per-worktree refs section. But
> lowercase head is known to not be a per-worktree ref, so we then ask
> the main worktree about head. Since you happen to be on a case
> insensitive file system, it then finds refs/HEAD in the main refs
> worktree, and returns that.
>
> I don't understand why the CentOS shows it as ambiguous, unless you
> actually happen to have a ref named head. (possibly a branch?)

I think it's just our default answer when we can't decide

$ git rev-parse head
head
fatal: ambiguous argument 'head': unknown revision or path not in the
working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'
$ git rev-parse head --
fatal: bad revision 'head'

> I suspect we could improve things by attempting to figure out if our
> file system is case insensitive and warn users. However, I recall
> patches which tried this, and no suitable method was found. Partly
> because it's not just "case" that is the only problem. There might be
> things like unicode characters which don't get properly encoded, etc.
>
> The best solution would be to get a non-filesystem backed ref storage
> working that could be used in place of the filesystem.

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

  reply	other threads:[~2018-12-14  7:38 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-13 19:54 [PATCH 0/1] " Michael Rappazzo via GitGitGadget
2018-12-13 19:54 ` [PATCH 1/1] " Michael Rappazzo via GitGitGadget
2018-12-13 20:23   ` Duy Nguyen
2018-12-13 20:34     ` Mike Rappazzo
2018-12-13 20:43       ` Duy Nguyen
2018-12-13 20:47         ` Stefan Beller
2018-12-13 21:14           ` Mike Rappazzo
2018-12-14  0:33             ` brian m. carlson
2018-12-14  6:49             ` Jacob Keller
2018-12-14  7:37               ` Duy Nguyen [this message]
2018-12-14 17:22                 ` Jacob Keller
2018-12-14 17:38                   ` Duy Nguyen
2018-12-14 17:46                     ` Duy Nguyen
2018-12-14 18:48                       ` Jacob Keller
2018-12-14 18:47                     ` Jacob Keller
2018-12-13 21:07         ` Mike Rappazzo
2018-12-14  3:31         ` Junio C Hamano
2018-12-14 10:36 ` [PATCH 0/1] " Johannes Schindelin

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