shell-completion-fignore

shell-completion-fignore is a variable defined in `shell.el'.
Its value is

nil

Documentation:
List of suffixes to be disregarded during file/command completion.
This variable is used to initialize `comint-completion-fignore' in the shell
buffer. The default is nil, for compatibility with most shells.
Some people like ("~" "#" "%").

You can customize this variable.