Re: check-attr doesn't respect recursive definitions

Jeff King [off-list ref] writes:

On Tue, Apr 02, 2013 at 09:43:30AM -0700, Junio C Hamano wrote:

quoted

quoted

In some systems, yes, but git does not have any notion of "doc/" as an
item (after all, we track content in files, not directories), so I do
not see what it means to specify a directory except to say "everything
under it has this property".

That was true back when gitattributes (and ignore) was defined to
apply only to the paths we track.  But export-ignore abuses the
attrtibute system, allows a directory to be specified in the match
pattern, and we declared that is a kosher use by the patch that
caused 1.8.1.X regression, no?  So "Git does not have any notion of
"doc/' as an item" is no longer true, I think.

Yes, but as I explained later, the meaning of "apply an attribute to
dir" in such cases is always equivalent to "apply attribute
recursively to dir/*". So I do not think we are violating that rule to
recursively apply all attributes.

I think this is where we disagree.  Attribute does not recursively
apply in general.  It was _never_ designed to (and that is the
authoritative answer, as I was who designed it in Apr 2007 ;-)).

It is not even true to say that "archive" applies export-ignore to
the directory recursively, with or without the recent change.  Would
it allow everything but dir/file to be excluded and still dir/file
to be included in the archive if you have a .gitattribute file like
this?

	dir/ export-ignore
        dir/file !export-ignore

I do not think so.

If we _were_ living in an alternate universe where we did not have
the .gitignore file and instead expressed what it does with an
"ignore" attribute, then having "dir" in the top-level .gitignore
file and "!file" in the .gitignore file in "dir/" directory may be
equivalent to having

	dir/ ignore
        dir/file -ignore

in your .gitattribute, and we would want to ignore dir/other while
including dir/file in the "may be interesting" paths.

The point is, yes, we could choose to define individual attribute
keys to apply recursively, but in general attributes were designed
not to recurse, and no existing attribute recurses.

But let's take a step back. I think Jan is trying to do a very
reasonable thing: come up with the same set of paths that git-archive
would. What's the best way to solve that?

Because the attribute does not recursively apply in general, and it
is entirely up to the application and a particular attribute key to
decide how the key is applied in the context of the application,
"check-attr" by itself cannot know.  You need to know how "archive"
treats "export-ignore" attribute and then use "check-attr" with that
knowledge.

Using:

  git ls-tree --name-only -zrt HEAD |
  git check-attr --stdin -z export-ignore

means we can find out that "foo/" is ignored.

Yes, and after learning that, we need to reject everything foo/*
using the knowledge that "git archive" cuts all subpaths of a path
that has "export-ignore" attribute is attached to.