Pathspec does not accept / does not warn for specific pathspecs

Hello there,

as I was trying to use git-archive to ... well, archive some artifacts. So I called: git archive HEAD -o p.zip --prefix=p/

Then, I noticed that .gitignore files from the repo were packed (and a couple of others, but we don't care about that right now). I wanted to exclude all .gitignore files (there is `/.gitignore` and `/resources/.gitignore`). So I did: git archive HEAD -o p.zip --prefix=p/ -- ':!.gitignore'

I noticed that the second-level .gitignore file was still included. I started thinking that this is not a .gitignore pathspec, but it matches a literal file. I don't know why at-the-time I accepted that, since, if I write `.ignoreFile` at a `.gitignore`, it would exclude any `.ignoreFile` at any level. So I did: git archive HEAD -o p.zip --prefix=p/ -- ':!/.gitignore'

Which, as expected, did not change anything; and I followed up with: git archive HEAD -o p.zip --prefix=p/ -- ':!**/.gitignore'

Then, I noticed some weird behavior. The second-level `.gitignore` was getting ignored, but not the first one! Someone at the chat indicated that, the `**` was _magically_ interpreted as `*`, which is obvious to me why it won't help. So, they suggested: git archive HEAD -o p.zip --prefix=p/ -- ':!(glob)**/.gitignore'

Which lead to **both of the .gitignores** to be included. And then I was baffled. Now I know (I guess) that the pathspec magic was `:!`, and I tried to match against a `(glob)**/.gitignore`, i.e. `(glob)*/.gitignore`, which, of course, it doesn't exist in any form.

And I wonder: Why doesn't `git archive ... -- ` understand `:!.gitignore` as a .gitignore file would do (minus the `:`)? Why doesn't `git archive ... -- ` understand `:!**/.gitignore` as a .gitignore file would do (minus the `:`)? Is there some reason that `git archive ... -- ` doesn't understand `:!(glob)**/.gitignore`? It doesn't sound awfully complicated, or risking a lot of regression (a folder starting with `(`, and containing valid pathspec long forms IMHO is rare), or Is there some reason that `git archive ... -- ` doesn't warn me that `:!(glob)**/.gitignore` is invalid (and maybe I meant `(exclude,glob)`)?

With regards, Ntentos Stavros