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:
>>> 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.