Re: [PATCH 0/6] Extensions of core.ignorecase=true support

From: Robert Buck <buck.robert.j@gmail.com>
Date: Aug 17, 2010, 19:36 UTC
Message-ID: <AANLkTi=0j_JFWBp=kJG6v+YBUxKAiVAVc4UtG0LWmipq@mail.gmail.com>
In-Reply-To: <cover.1281985411.git.j6t@kdbg.org>

While I tend to agree with case-insensitive searches, I would tend to question the use of a non-case-preserving / last-use methodology reminiscent of the days of DOS. I was never terribly fond of DOS nor of Windows for Workgroups, and this change smacks of that. That said, as an algorithm it is one legitimate option, I just would not tend to use it.

Have you thought of other approaches that are case-preserving / case-insensitive (modern Windows implementations and Mac OS X) or of case-sensitive (UNIX)? What about giving the user the choice?

Looking back at how flexible and simple folks here on this list made the EOL support (the best I have seen to date) what if you followed a similar approach and provided the flexibility to the users by giving the options to control the behavior themselves, then fall back to reasonable defaults if left unspecified?

I would imagine having two properties would be somewhat more useful:

core.casepreserving=true|false core.caseinsensitive=true|false

For Unix-centric environments the defaults would be true & false, respectively. For mixed Windows/Unix environments users would configure it as true & true. A combination of false & true, respectively, would be appropriate for DOS users, but this may be another option for mixed environments. A combination of false & false would be impossible by definition.

What this would mean is that searches in the purely Unix world would store and match sensitively; but in such an environment there may be issues should any Windows users attempt to work with the repository if two files having a similar names existed. For Windows users the last read operation would overwrite the first (not a good thing).

For mixed configurations there are two options, the Windows/Mac option, and the DOS option.

The nice thing about case-insensitivity is that when requesting a file by name any capitalization can be used. The bad thing, well come to think of it, there is none that I can think of, but for those more religious than I about Unix they may cite otherwise.

-Bob

On Mon, Aug 16, 2010 at 3:38 PM, Johannes Sixt <j6t@kdbg.org> wrote:

Show 52 quoted lines

> The following patch series extends the core.ignorecase=true support to
> handle case insensitive comparisons for the .gitignore file, git status,
> and git ls-files.  git add and git fast-import will fold the case of the
> file being added, matching that of an already added directory entry.  Case
> folding is also applied to git fast-import for renames, copies, and deletes.
>
> The most notable benefit, IMO, is that the case of directories in the
> worktree does not matter if, and only if, the directory exists already in
> the index with some different case variant.  This helps applications on
> Windows that change the case even of directories in unpredictable ways.
> Joshua mentioned Perforce as the primary example.
>
> Concerning the implementation, Joshua explained when he initially submitted
> the series to the msysgit mailing list:
>
>  git status and add both use an update made to name-hash.c where
>  directories, specifically names with a trailing slash, can be looked up
>  in a case insensitive manner. After trying a myriad of solutions, this
>  seemed to be the cleanest. Does anyone see a problem with embedding the
>  directory names in the same hash as the file names? I couldn't find one,
>  especially since I append a slash to each directory name.
>
>  The git add path case folding functionality is a somewhat radical
>  departure from what Git does now. It is described in detail in patch 5.
>  Does anyone have any concerns?
>
> I support the idea of this patch, and I can confirm that it works: I've
> used this series in production both with core.ignorecase set to true and
> to false, and in the former case, with directories and files with case
> different from the index.
>
> Joshua Jensen (6):
>  Add string comparison functions that respect the ignore_case
>    variable.
>  Case insensitivity support for .gitignore via core.ignorecase
>  Add case insensitivity support for directories when using git status
>  Add case insensitivity support when using git ls-files
>  Support case folding for git add when core.ignorecase=true
>  Support case folding in git fast-import when core.ignorecase=true
>
>  dir.c         |  105 ++++++++++++++++++++++++++++++++++++++++++++++----------
>  dir.h         |    4 ++
>  fast-import.c |    7 ++--
>  name-hash.c   |   72 ++++++++++++++++++++++++++++++++++++++-
>  read-cache.c  |   23 ++++++++++++
>  5 files changed, 188 insertions(+), 23 deletions(-)
>
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