Feature request: Set a default completion function

[albers]

In my experience, not many flags actually require completion of files.

Some have dynamic completions, but a great deal of them take free-form string parameters where no completion can be offered. Unfortunately, the default completion for a flag with no completion function in Cobra is file completion. This forces me to register a cobra.NoFileCompletions for each flag of that category.

As an example, completion for docker run has 56 flags where no meaningful FlagCompletionFunc exists. In a first attempt, I registered 56 handlers with cmd.RegisterFlagCompletionFunc("flag-name", cobra.NoFileCompletions) just to silence their file completion. Following a hint of @thaJeztah, I replaced them with a programmatically installed default handler, see here.

I would very much welcome a solution in Cobra, where I can set a default handler on command level, something like

cmd.CompletionOptions.DefaultCompHandler = cobra.NoFileCompletions

With this feature, I'd only have to define the completion functions for flags that actually have meaningful completions.

/cc @thaJeztah