Re: git 2.34.0: Behavior of `**` in gitignore is different from previous versions.

On 11/19/2021 3:05 PM, Johannes Sixt wrote:

Am 19.11.21 um 15:51 schrieb Derrick Stolee:

quoted

What is unclear to me is what exactly "match a directory" means.
If we ignore a directory, then we ignore everything inside it (until
another pattern says we should care about it), but the converse
should also hold: if we have a pattern like "!data/**/", then that
should mean "include everything inside data/<A>/ where <A> is any
directory name".

My inability to form a mental model where the existing behavior
matches the documented specification is an indicator that this was
changed erroneously. A revert patch is included at the end of this
message.

If anyone could help clarify my understanding here, then maybe
there is room for improving the documentation.

You form a wrong mental model when you start with the grand picture of a
working tree. That is, when you say

- here I have theeeeeese many files and directories,
- and I want to ignore some: foo/**/,
- but I don't want to ignore others: !bar/**/.

This forms the wrong mental model because that is not how Git sees the
working tree: it never has a grand picture of all of its contents.

Git only ever sees the contents of one directory. When Git determines
that a sub-directory is ignored, then that one's contents are never
inspected, and there is no opportunity to un-ignore some of the
sub-directory's contents.

So the problem is this: I want to know "I have a file named <X>, and
a certain pattern set, does <X> match the patterns or not?" but in
fact it's not just "check <X> against the patterns in order" but
actually "check every parent directory of <X> in order to see if
any directory is unmatched, which would preclude any later matches
to other parents of <X>"

So really, to check a path, we really want to first iterate on the
parent directories. If we get a match on a positive pattern on level
i, then we check level (i+1) for a match on a negative pattern. If
we find that negative pattern match, then continue. If we do not see
a negative match, then we terminate by matching the entire path <X>.

I'm still not seeing a clear way of describing the matching procedure
here for a single path, and that's fine. Me understanding is not a
necessary condition for fixing this bug.

Thanks,
-Stolee