If the argument to make_file can act like a file, return it. This is useful for code that calls command functions, but doesn't want to send I/O through the filesystem.

\.orig$
\.rej$
~$
\.so$
\.pyc$
\.swp$
^build/
^dist/
^doc/.*\.[0-9]$
^MANIFEST$
^.pc/
^patches/
^mercurial/__version__.py$