Re: [PATCH] Fix "inside work tree" detection on case-insensitive filesystems

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Jan 1, 2016, 14:58 UTC
Message-ID: <alpine.DEB.2.20.1601011554240.14434@virtualbox>
In-Reply-To: <56829D08.1060107@alum.mit.edu>

Hi Michael,

On Tue, 29 Dec 2015, Michael Haggerty wrote:

Show 16 quoted lines

> On 09/28/2015 06:12 PM, Johannes Schindelin wrote:
> > Git has a config variable to indicate that it is operating on a file
> > system that is case-insensitive: core.ignoreCase. But the
> > `dir_inside_of()` function did not respect that. As a result, if Git's
> > idea of the current working directory disagreed in its upper/lower case
> > with the `GIT_WORK_TREE` variable (e.g. `C:\test` vs `c:\test`) the
> > user would be greeted by the error message
> > 
> > 	fatal: git-am cannot be used without a working tree.
> > 
> > when trying to run a rebase.
> > 
> > This fixes https://github.com/git-for-windows/git/issues/402 (reported by
> > Daniel Harding).
> 
> I was just going through the 2.7 release notes when I saw this patch.

Thanks for your diligence!

Show 6 quoted lines

> My understanding was that many of the case-insensitive filesystems also
> support Unicode. Is the byte-oriented code in this patch adequate? I
> would have thought it necessary to use a Unicode-aware algorithm here,
> that knows:
> 
> * that bytes != characters

I am not sure that we can in general assume that the file name is UTF-8... Or does Git always assume that?

> * how to do a case-insensitive comparison of strings that include
> non-ASCII characters

I was worrying about that, too, but decided to punt on it when I realized that no other case-insensitive code in Git bothers about those characters.

> * (possibly) insensitivity to NFC vs. NFD vs. non-normalized forms

Whoa... I really would like to stay away from that collection of potholes...

> I suppose that such OSs have built-in functions for deciding whether two
> paths are equivalent. Possibly these could be used?

We could, in theory, try to do that, but what about the OSes that do *not* have those functions? We would need our own fallback anyway, so why not guarantee consistency and use our own functions only?

Ciao, Dscho