Ability to autocomplete filename

[ws1088]

would be nice to do auto complete of filenames, like ipython. if we don't want to do this in general context, maybe we can do this when specifying the value of the click file type option?

[KSchopmeyer]

For click8 at least, I would assume use of tab completion for file or path would based this on the same criteria as the tab-completion for directories and files, the type attribute of the option/argument decorator. Thus type=click.Path(. . .). The goal in our project is to keep tab-completion as similar as possible between the repl mode and the tab-completion available with the shell, at least the bash shell.