What's with the …file suffix in file names?!

We have Dockerfile, Makefile, Caddyfile, Gemfile, Rakefile, Vagrantfile, Cakefile and probably a lot more that …file files that I’ve yet to come across.

Dear config file inventor: I know they are files! My terminal even shows directories in a different color!

What’s wrong with traditional file extensions? How about docker.conf?

What’s next? logdirectory/, datadirectory/, srcdirectory/?

Please, no more file names from the Department of Redundancy Department!