cli: disable file-completion by default

This uses the DefaultShellCompDirective feature which was added
in cobra to override the default (which would complete to use
files for commands and flags).

Note that we set "cobra.NoFileCompletions" for many commands, which
is redundant with this change, so we could remove as well.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/container/run.go

@@ -76,13 +76,6 @@ func newRunCommand(dockerCLI command.Cli) *cobra.Command {
 	_ = cmd.RegisterFlagCompletionFunc("detach-keys", completeDetachKeys)
 	addCompletions(cmd, dockerCLI)
 
-	flags.VisitAll(func(flag *pflag.Flag) {
-		// Set a default completion function if none was set. We don't look
-		// up if it does already have one set, because Cobra does this for
-		// us, and returns an error (which we ignore for this reason).
-		_ = cmd.RegisterFlagCompletionFunc(flag.Name, cobra.NoFileCompletions)
-	})
-
 	return cmd
 }