[RFC] Case insensitive Git attributes

Hi,

Git attributes for path names are generally case sensitive. However, on a case insensitive file system (e.g. macOS/Windows) they appear to be case insensitive (`*.bar` would match `foo.bar` and `foo.BAR`). That works great until a Git users joins the party with a case sensitive file system. For this Git user only files that match the exact case of the attribute pattern get the attributes (only `foo.bar`).

This inconsistent behavior can confuse Git users. An advanced Git user could use a glob pattern (e.g. `*.[bB][aA][rR]) to match files in a case insensitive way. However, this can get confusing quickly, too.

I wonder if we can do something about this. One idea could be to add an attribute "case-sensitive" (or "caseSensitive") and set it to false (if desired) for all files in .gitattributes for a given repo.

### .gitattributes example ###

* case-sensitive=false
*.bar something

###

I haven't looked into the feasibility of an implementation, yet. However, would that be an acceptable approach?

Thanks, Lars

On Sun, Oct 16, 2016 at 6:04 PM, Lars Schneider <larsxschneider@gmail.com> wrote:

FYI: I am currently refactoring the attr subsystem (e.g.
https://public-inbox.org/git/20161012224109.23410-1-sbeller@google.com/
"attr: convert to new threadsafe API")

Would this modify the current file only or the whole stack of attrs? (In just one way or the whole stack, i.e. can you add this in .git/info/exclude and the attribute file in the home dir also behaves differently? Or rather the other way round when the system wide attr file enables case insensitivity, each repository local config is set automatically? both ways?)

Conceptually I would prefer if we had a single switch that indicates a case insensitive FS. That could be used for different purposes as well, that are FS relevant such as checking in, checking out/renaming files in the working tree? (does any such switch already exist for case sensitivity?)

Thanks, Stefan

On 17/10/16 05:07, Stefan Beller wrote:

This feels like a bug:

$ git diff

Hi Stefan,

On Sun, 16 Oct 2016, Stefan Beller wrote:

AFAIU Lars' use case is where the FS is *case sensitive*, but he still needs the .gitattributes to be *case insensitive* because that file originates from a developer with such a file system.

Otherwise he would simply tack onto the core.ignoreCase flag.

Ciao, Dscho

On Mon, Oct 17, 2016 at 3:57 PM, Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:

That sounds to me like setting core.ignoreCase to true (on all devs' repo) would "solve" this. Yes core.ignoreCase may introduce some side effects when used on case-sensitive filesystems, so we probably want something in the same spirit but limited to .gitattributes and .gitignore only.

Hi Duy,

On Mon, 17 Oct 2016, Duy Nguyen wrote:

It is good that you quoted this verb, because it does not solve things. Instead, it would try to use the flag for two slightly incompatible purposes at the same time.

The first (and so far, only) purpose is to tell Git that the current file system is case insensitive.

The new purpose you described would be to tell Git that the *user* does not care about the file names' case, even if the file system does.

I do not think that this leads to a better situation than before. Instead, I am convinced that it will cause new and sometimes "entertaining" problems because you can no longer discern between those two purposes based on core.ignoreCase, you would have to teach Git to test every single time whether the file system is case-sensitive or not.

Needless to say, I'd rather not see that happening. Many users, including my colleagues and myself, rely on Git being a rock solid piece of software, and that change would make it less so.

Ciao, Dscho

On Mon, Oct 17, 2016 at 5:46 PM, Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:

I agree. Which is why I wrote "we probably want something in the same spirit but limited to .gitattributes and .gitignore only". In other words we could have core.someName that makes .gitattributes and .gitignore patterns case-insensitive (or core-sensitive). If it's present, it overrides core.ignoreCase. If it's not present, core.ignoreCase decides. I'm just not sure if the new config should cover everything involving filename's case in git. That's too big to fit in my head.

Duy Nguyen <pclouds@gmail.com> writes:

Once I stopped thinking about this as "filename's case", it does fit my head ;-)

I view the proposed knob as making patterns in .gitattributes and .gitignore case insensitive, iow, it is a lazy and useful short-hand for (mentally) editing "*.c attr" to "*.[cC] attr" without touching these files.

And I agree that the knob that is missing in today's Git should default to whatever core.ignoreCase's value is, iow, on case insensitive filesystem, attr and ignore may match case insensitively in today's Git, but when the knob is introduced, it should allow forcing case sensitive match there by setting it to false, just like the knob is proposed to be used in the oppositite direction to force case insensitive match regardless of the case insensitiveness of the underlying filesystem.

Hi Lars,

On Sun, 16 Oct 2016, Lars Schneider wrote:

Hrm. Maybe a better idea would be to warn when attributes match a file name with a different case?

Ciao, Dscho