On Tue, Jan 5, 2016 at 10:06 PM, Jeff King [off-list ref] wrote:

On Tue, Jan 05, 2016 at 02:40:16PM +0000, Mike McQuaid wrote:

quoted

Homebrew has a series of convoluted .gitignore rules due to our
special/weird use-case of wanting to ignore everything in a working
directory except a select few files/directories. We experienced a bug
with our .gitignore file for users using Git 2.7.0. This may well be a
valid WONTFIX or intentional behaviour change but I wanted to flag it
in case it wasn’t.

Here’s a minimal test case:

- Create an empty git repository in a directory with `git init`
- Create a directory named ‘a' containing a file named ‘b' with `mkdir a && touch a/b`
- Create a ‘gitignore’ file with the following contents:

*/
/a
!/a/*

- Run `git status --short`.

The output with Git 2.6.4 is:

?? .gitignore

The output with Git 2.7.0 is:

?? .gitignore
?? a/

Thanks for giving a clear example. This bisects to Duy's 57534ee (dir.c:
don't exclude whole dir prematurely if neg pattern may match,
2015-09-21). AFAICT (and I don't recall looking over this patch
previously), what you are seeing is the intended effect of the patch.

Yeah.. I think it's the only relevant commit in 2.7.0 cycle anyway.
These patterns "/a" followed by "!/a/*" were wrecking my head. But I
finally decided 2.7 output makes more sense. You asked to un-ignore
everything inside 'a' so we can't treat 'a' as (entirely) ignored and
hide it away.

I'm sympathetic that in making that use-case work, we might have
regressed another one, but it's hard to tell from the small example. Can
you elaborate on your use case? Why are you both ignoring and unignoring
everything in the directory?

Also how bad this affects you (widely-used 'wrong' behavior can become
'right', and my change a regression as a result)
-- 
Duy