When I create a folder and name it "test.tmp" the finder asks me if I want to add the file extension ".tmp" to my folder. When accepted, the folder changes to a document with an icon.
I then can no longer open the 'folder' by double clicking on it. There is no default application associated to open the test.tmp file.
If I run ls -l the file is still shown as a directory.
On another Mac I am able to create this same folder name, and the folder remains a folder.
Any idea why on my Mac adding the .tmp changes the folder to a file?