On Fri, Jan 8, 2016 at 6:44 AM, brian m. carlson
[off-list ref] wrote:

On Tue, Jan 05, 2016 at 10:06:02AM -0500, Jeff King wrote:

quoted

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.

Your final line unignores stuff inside of "a", so we're reporting it (if you gave
"-uall", you'd see the actual file "a/b"). Older versions of git
generally optimized out looking inside "a/" at all. This created a
hassle when people wanted to do things like:

    a/
    !a/precious-file

in their .gitignore.

I think there's still a bug in the code here.  If you do

  git init
  mkdir -p base/a/
  printf 'base/a/\n!base/a/b.txt\n' >.gitignore

Here we have the ignore rule "base/a/", but gitignore.txt, section
NOTES mentions this

 - The rules to exclude the parent directory must not end with a
   trailing slash.

  git add .gitignore
  git commit -m 'Add .gitignore'
  >base/a/b.txt
  git add base/a/b.txt
  git commit -m 'Add base/a/b.txt'
  >base/a/c.txt
  git status --porcelain

git status outputs base/a/c.txt as unknown, when it should be ignored.
We saw this in a repository at $DAYJOB.

If I delete that trailing slash, c.txt is ignored. So it's known
limitation. I think we can make trailing slash case work too, but if I
remember correctly it would involve a lot more changes, so I didn't do
it (there are other conditions to follow anyway to make it work).
-- 
Duy