Bug with the --exclude option for pr diff

### Describe the bug

When doing: `gh pr diff 123 --name-only --exclude '*.md'` only the first two file names are printed.

### Affected version

gh version 2.88.1 (2026-03-12)
https://github.com/cli/cli/releases/tag/v2.88.1

### Steps to reproduce the behavior

1. Type this `gh pr diff 123 --name-only --exclude '*.md'`
2. View the output ''
3. See error - incorrect behaviour in that no glob pattern actually works.

### Expected vs actual behavior

When using the `--exclude` option for `pr diff ..` I expect some files to be excluded, but the behaviour is irratic.

### Logs

N/A.