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

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What did you do before the bug happened? (Steps to reproduce your issue)
Consider the following project structure
- data
  - data1
    - file1
    - file1.txt
  - data2
    - file2
    - file2.txt
- .gitignore

`.gitignore` is as follows: ``` data/** !data/**/ !data/**/*.txt ``` What did you expect to happen? (Expected behavior)

I expect all files in `data` folder to be ignored except `.txt` files.

What happened instead? (Actual behavior)

`file1` and `file2` are not ignored. Here is the `check-ignore` output: ``` $ git check-ignore -v data/data1/file1 .gitignore:2:!/data/**/ data/data1/file1 ```

What's different between what you expected and what actually happened? It seems that the behavior of `**` in gitignore is different from previous versions.

Anything else you want to add:

Please review the rest of the bug report below. You can delete any lines you don't wish to share.

[System Info] git version: git version 2.34.0 cpu: x86_64 no commit associated with this build sizeof-long: 8 sizeof-size_t: 8 shell-path: /bin/sh uname: Linux 5.15.2-arch1-1 compiler info: gnuc: 11.1 libc info: glibc: 2.33 $SHELL (typically, interactive shell): /usr/bin/zsh

[Enabled Hooks]