cli: improve argument validation output

Improve the output for these validation errors:

- Removes the short command description from the output. This information
  does not provide much useful help, and distracts from the error message.
- Reduces punctuation, and
- Prefixes the error message with the binary / root-command name
  (usually `docker:`) to be consistent with other similar errors.
- Adds an empty line between the error-message and the "call to action"
  (`Run 'docker volume --help'...` in the example below). This helps
  separating the error message and "usage" from the call-to-action.

Before this patch:

    $ docker volume ls one two three
    "docker volume ls" accepts no arguments.
    See 'docker volume ls --help'.

    Usage:  docker volume ls [OPTIONS]

    List volumes

    $ docker volume create one two three
    "docker volume create" requires at most 1 argument.
    See 'docker volume create --help'.

    Usage:  docker volume create [OPTIONS] [VOLUME]

    Create a volume

With this patch:

    $ docker volume ls one two three
    docker: 'docker volume ls' accepts no arguments

    Usage:  docker volume ls [OPTIONS]

    Run 'docker volume ls --help' for more information

    $ docker voludocker volume create one two three
    docker: 'docker volume create' requires at most 1 argument

    Usage:  docker volume create [OPTIONS] [VOLUME]

    SRun 'docker volume create --help' for more information

Signed-off-by: Sebastiaan van Stijn <[email protected]>

cli/required.go

@@ -22,11 +22,10 @@ func NoArgs(cmd *cobra.Command, args []string) error {
 	}
 
 	return errors.Errorf(
-		"%q accepts no arguments.\nSee '%s --help'.\n\nUsage:  %s\n\n%s",
-		cmd.CommandPath(),
+		"%[1]s: '%[2]s' accepts no arguments\n\nUsage:  %[3]s\n\nRun '%[2]s --help' for more information",
+		binName(cmd),
 		cmd.CommandPath(),
 		cmd.UseLine(),
-		cmd.Short,
 	)
 }
 
@@ -37,13 +36,12 @@ func RequiresMinArgs(min int) cobra.PositionalArgs {
 			return nil
 		}
 		return errors.Errorf(
-			"%q requires at least %d %s.\nSee '%s --help'.\n\nUsage:  %s\n\n%s",
+			"%[1]s: '%[2]s' requires at least %[3]d %[4]s\n\nUsage:  %[5]s\n\nSee '%[2]s --help' for more information",
+			binName(cmd),
 			cmd.CommandPath(),
 			min,
 			pluralize("argument", min),
-			cmd.CommandPath(),
 			cmd.UseLine(),
-			cmd.Short,
 		)
 	}
 }
@@ -55,13 +53,12 @@ func RequiresMaxArgs(max int) cobra.PositionalArgs {
 			return nil
 		}
 		return errors.Errorf(
-			"%q requires at most %d %s.\nSee '%s --help'.\n\nUsage:  %s\n\n%s",
+			"%[1]s: '%[2]s' requires at most %[3]d %[4]s\n\nUsage:  %[5]s\n\nSRun '%[2]s --help' for more information",
+			binName(cmd),
 			cmd.CommandPath(),
 			max,
 			pluralize("argument", max),
-			cmd.CommandPath(),
 			cmd.UseLine(),
-			cmd.Short,
 		)
 	}
 }
@@ -73,14 +70,13 @@ func RequiresRangeArgs(min int, max int) cobra.PositionalArgs {
 			return nil
 		}
 		return errors.Errorf(
-			"%q requires at least %d and at most %d %s.\nSee '%s --help'.\n\nUsage:  %s\n\n%s",
+			"%[1]s: '%[2]s' requires at least %[3]d and at most %[4]d %[5]s\n\nUsage:  %[6]s\n\nRun '%[2]s --help' for more information",
+			binName(cmd),
 			cmd.CommandPath(),
 			min,
 			max,
 			pluralize("argument", max),
-			cmd.CommandPath(),
 			cmd.UseLine(),
-			cmd.Short,
 		)
 	}
 }
@@ -92,13 +88,12 @@ func ExactArgs(number int) cobra.PositionalArgs {
 			return nil
 		}
 		return errors.Errorf(
-			"%q requires exactly %d %s.\nSee '%s --help'.\n\nUsage:  %s\n\n%s",
+			"%[1]s: '%[2]s' requires %[3]d %[4]s\n\nUsage:  %[5]s\n\nRun '%[2]s --help' for more information",
+			binName(cmd),
 			cmd.CommandPath(),
 			number,
 			pluralize("argument", number),
-			cmd.CommandPath(),
 			cmd.UseLine(),
-			cmd.Short,
 		)
 	}
 }