On case-insensitive filesystem the -include option may create false duplicates

[scrubbbbs]

-include folder seems to use "folder" when the folder name is "Folder". A later index w/o -include will use "Folder" and create duplicates in the index.

Originally posted by @scrubbbbs in https://github.com/scrubbbbs/cbird/discussions/32#discussioncomment-12806778