I’m sure there’s an order-of-include/exclude solution to this, but I want to sync a home directory for a user which has a mail folder. I do not want the mail folder, but if there happens to be another subfolder with the same name, I need that included.

For instance, a source directory with this structure:

mkdir -p {foo/mail,foo/public/mail}
touch {foo/mail/this,foo/public/that,foo/public/mail/theother}

foo
 |- mail
 |   - this
 - public
     |- that
     - mail
         - theother

… with this rsync command to exclude the mail folder…

rsync -avP --exclude="mail/" foo/ bar

… creates the following bar folder:

bar
 - public
     - that

I need to include that public/mail folder WITHOUT prior knowledge of its presence, since I am not in control of its contents. Syncing the public folder separately is also not feasible, since this is only an example; the foo folder could contain countless unknown folders and files. I only know for certain that I want to exclude the mail folder from the root of my sync source.