fix: propagate leading --help to subcommands with a local help flag

- --help before a subcommand is parsed as the root's persistent flag and
  stripped from args, which works for most subcommands since they share
  the same flag object with root
- run/create register their own local help flag (no -h, to avoid a
  shorthand clash with --hostname), which shadows root's and never saw
  the value, so the container ran instead of printing usage
- propagate the parsed value into a subcommand's local help flag when
  one shadows the root's, in HandleGlobalFlags

Fixes #7473

Signed-off-by: Nick Sieger <nick@nicksieger.com>

cli/cobra.go

@@ -160,7 +160,25 @@ func (tcmd *TopLevelCommand) HandleGlobalFlags() (*cobra.Command, []string, erro
 		return nil, nil, cmd.FlagErrorFunc()(cmd, err)
 	}
 
-	return cmd, flags.Args(), nil
+	args := flags.Args()
+
+	// A leading "--help"/"-h" is consumed above as the root's persistent
+	// help flag and stripped from args, so the target subcommand never sees
+	// it. That's fine for most subcommands, which inherit the same help
+	// flag instance, but "run" and "create" register their own local
+	// "help" flag (to avoid a shorthand clash with "-h"/"--hostname"),
+	// which shadows the persistent one and is left false. Propagate the
+	// value so "docker --help run <image>" shows help like "docker run
+	// --help" does, instead of running the container.
+	if help, _ := flags.GetBool("help"); help {
+		if sub, _, err := cmd.Find(args); err == nil && sub != cmd {
+			if sub.Flags().Lookup("help") != nil {
+				_ = sub.Flags().Set("help", "true")
+			}
+		}
+	}
+
+	return cmd, args, nil
 }
 
 // Initialize finalises global option parsing and initializes the docker client.

cli/cobra_test.go

@@ -108,3 +108,45 @@ func TestDecoratedName(t *testing.T) {
 	topLevelCommand.Annotations = map[string]string{metadata.CommandAnnotationPlugin: "true"}
 	assert.Equal(t, decoratedName(topLevelCommand), "pluginTopLevelCommand*")
 }
+
+// TestHandleGlobalFlagsHelpPropagation covers https://github.com/docker/cli/issues/7473:
+// a leading "--help" is consumed as the root's persistent help flag and
+// stripped from args, so a subcommand that registers its own local "help"
+// flag (as "run" and "create" do, to avoid a shorthand clash with "-h") never
+// sees it and runs instead of showing help.
+func TestHandleGlobalFlagsHelpPropagation(t *testing.T) {
+	newRootCmd := func() (root, sub *cobra.Command) {
+		root = &cobra.Command{Use: "docker"}
+		root.PersistentFlags().BoolP("help", "h", false, "Print usage")
+
+		sub = &cobra.Command{Use: "run", RunE: func(cmd *cobra.Command, args []string) error { return nil }}
+		sub.Flags().Bool("help", false, "Print usage")
+		root.AddCommand(sub)
+		return root, sub
+	}
+
+	t.Run("propagates to the shadowing local help flag", func(t *testing.T) {
+		root, sub := newRootCmd()
+		tcmd := &TopLevelCommand{cmd: root, args: []string{"--help", "run", "hello-world"}}
+
+		_, args, err := tcmd.HandleGlobalFlags()
+		assert.NilError(t, err)
+		assert.DeepEqual(t, args, []string{"run", "hello-world"})
+
+		help, err := sub.Flags().GetBool("help")
+		assert.NilError(t, err)
+		assert.Equal(t, help, true)
+	})
+
+	t.Run("leaves the local help flag alone without --help", func(t *testing.T) {
+		root, sub := newRootCmd()
+		tcmd := &TopLevelCommand{cmd: root, args: []string{"run", "hello-world"}}
+
+		_, _, err := tcmd.HandleGlobalFlags()
+		assert.NilError(t, err)
+
+		help, err := sub.Flags().GetBool("help")
+		assert.NilError(t, err)
+		assert.Equal(t, help, false)
+	})
+}