move commonly used top-level commands to the top of --help

This adds a new annotation to commands that are known to be frequently
used, and allows setting a custom weight/order for these commands to
influence in what order they appear in the --help output.

I'm not entirely happy with the implementation (we could at least use
some helpers for this, and/or make it more generic to group commands
in output), but it could be a start.

For now, limiting this to only be used for the top-level --help, but
we can expand this to subcommands as well if we think it makes sense
to highlight "common" / "commonly used" commands.

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

cli/command/container/exec.go

@@ -52,6 +52,9 @@ func NewExecCommand(dockerCli command.Cli) *cobra.Command {
 			options.Command = args[1:]
 			return RunExec(dockerCli, options)
 		},
+		Annotations: map[string]string{
+			"category-top": "2",
+		},
 	}
 
 	flags := cmd.Flags()