Create a struct with all of Hugo's config options

Primary motivation is documentation, but it will also hopefully simplify the code.

Also,

* Lower case the default output format names; this is in line with the custom ones (map keys) and how
it's treated all the places. This avoids doing `stringds.EqualFold` everywhere.

Closes #10896
Closes #10620

commands/gen.go

@@ -1,4 +1,4 @@
-// Copyright 2015 The Hugo Authors. All rights reserved.
+// Copyright 2023 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -14,27 +14,200 @@
 package commands
 
 import (
+	"context"
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+
+	"github.com/alecthomas/chroma/v2"
+	"github.com/alecthomas/chroma/v2/formatters/html"
+	"github.com/alecthomas/chroma/v2/styles"
+	"github.com/bep/simplecobra"
+	"github.com/gohugoio/hugo/common/hugo"
+	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/hugofs"
 	"github.com/spf13/cobra"
+	"github.com/spf13/cobra/doc"
 )
 
-var _ cmder = (*genCmd)(nil)
+func newGenCommand() *genCommand {
+	var (
+		// Flags.
+		gendocdir string
+		genmandir string
+
+		// Chroma flags.
+		style          string
+		highlightStyle string
+		linesStyle     string
+	)
+
+	newChromaStyles := func() simplecobra.Commander {
+		return &simpleCommand{
+			name:  "chromastyles",
+			short: "Generate CSS stylesheet for the Chroma code highlighter",
+			long: `Generate CSS stylesheet for the Chroma code highlighter for a given style. This stylesheet is needed if markup.highlight.noClasses is disabled in config.
+
+See https://xyproto.github.io/splash/docs/all.html for a preview of the available styles`,
+
+			run: func(ctx context.Context, cd *simplecobra.Commandeer, r *rootCommand, args []string) error {
+				builder := styles.Get(style).Builder()
+				if highlightStyle != "" {
+					builder.Add(chroma.LineHighlight, highlightStyle)
+				}
+				if linesStyle != "" {
+					builder.Add(chroma.LineNumbers, linesStyle)
+				}
+				style, err := builder.Build()
+				if err != nil {
+					return err
+				}
+				formatter := html.New(html.WithAllClasses(true))
+				formatter.WriteCSS(os.Stdout, style)
+				return nil
+			},
+			withc: func(cmd *cobra.Command) {
+				cmd.PersistentFlags().StringVar(&style, "style", "friendly", "highlighter style (see https://xyproto.github.io/splash/docs/)")
+				cmd.PersistentFlags().StringVar(&highlightStyle, "highlightStyle", "bg:#ffffcc", "style used for highlighting lines (see https://github.com/alecthomas/chroma)")
+				cmd.PersistentFlags().StringVar(&linesStyle, "linesStyle", "", "style used for line numbers (see https://github.com/alecthomas/chroma)")
+			},
+		}
+	}
+
+	newMan := func() simplecobra.Commander {
+		return &simpleCommand{
+			name:  "man",
+			short: "Generate man pages for the Hugo CLI",
+			long: `This command automatically generates up-to-date man pages of Hugo's
+	command-line interface.  By default, it creates the man page files
+	in the "man" directory under the current directory.`,
+
+			run: func(ctx context.Context, cd *simplecobra.Commandeer, r *rootCommand, args []string) error {
+				header := &doc.GenManHeader{
+					Section: "1",
+					Manual:  "Hugo Manual",
+					Source:  fmt.Sprintf("Hugo %s", hugo.CurrentVersion),
+				}
+				if !strings.HasSuffix(genmandir, helpers.FilePathSeparator) {
+					genmandir += helpers.FilePathSeparator
+				}
+				if found, _ := helpers.Exists(genmandir, hugofs.Os); !found {
+					r.Println("Directory", genmandir, "does not exist, creating...")
+					if err := hugofs.Os.MkdirAll(genmandir, 0777); err != nil {
+						return err
+					}
+				}
+				cd.CobraCommand.Root().DisableAutoGenTag = true
+
+				r.Println("Generating Hugo man pages in", genmandir, "...")
+				doc.GenManTree(cd.CobraCommand.Root(), header, genmandir)
+
+				r.Println("Done.")
+
+				return nil
+			},
+			withc: func(cmd *cobra.Command) {
+				cmd.PersistentFlags().StringVar(&genmandir, "dir", "man/", "the directory to write the man pages.")
+				// For bash-completion
+				cmd.PersistentFlags().SetAnnotation("dir", cobra.BashCompSubdirsInDir, []string{})
+			},
+		}
+	}
+
+	newGen := func() simplecobra.Commander {
+		const gendocFrontmatterTemplate = `---
+title: "%s"
+slug: %s
+url: %s
+---
+`
+
+		return &simpleCommand{
+			name:  "doc",
+			short: "Generate Markdown documentation for the Hugo CLI.",
+			long: `Generate Markdown documentation for the Hugo CLI.
+			This command is, mostly, used to create up-to-date documentation
+	of Hugo's command-line interface for https://gohugo.io/.
+	
+	It creates one Markdown file per command with front matter suitable
+	for rendering in Hugo.`,
+			run: func(ctx context.Context, cd *simplecobra.Commandeer, r *rootCommand, args []string) error {
+				cd.CobraCommand.VisitParents(func(c *cobra.Command) {
+					// Disable the "Auto generated by spf13/cobra on DATE"
+					// as it creates a lot of diffs.
+					c.DisableAutoGenTag = true
+				})
+				if !strings.HasSuffix(gendocdir, helpers.FilePathSeparator) {
+					gendocdir += helpers.FilePathSeparator
+				}
+				if found, _ := helpers.Exists(gendocdir, hugofs.Os); !found {
+					r.Println("Directory", gendocdir, "does not exist, creating...")
+					if err := hugofs.Os.MkdirAll(gendocdir, 0777); err != nil {
+						return err
+					}
+				}
+				prepender := func(filename string) string {
+					name := filepath.Base(filename)
+					base := strings.TrimSuffix(name, path.Ext(name))
+					url := "/commands/" + strings.ToLower(base) + "/"
+					return fmt.Sprintf(gendocFrontmatterTemplate, strings.Replace(base, "_", " ", -1), base, url)
+				}
+
+				linkHandler := func(name string) string {
+					base := strings.TrimSuffix(name, path.Ext(name))
+					return "/commands/" + strings.ToLower(base) + "/"
+				}
+				r.Println("Generating Hugo command-line documentation in", gendocdir, "...")
+				doc.GenMarkdownTreeCustom(cd.CobraCommand.Root(), gendocdir, prepender, linkHandler)
+				r.Println("Done.")
+
+				return nil
+			},
+			withc: func(cmd *cobra.Command) {
+				cmd.PersistentFlags().StringVar(&gendocdir, "dir", "/tmp/hugodoc/", "the directory to write the doc.")
+				// For bash-completion
+				cmd.PersistentFlags().SetAnnotation("dir", cobra.BashCompSubdirsInDir, []string{})
+			},
+		}
+
+	}
+
+	return &genCommand{
+		commands: []simplecobra.Commander{
+			newChromaStyles(),
+			newGen(),
+			newMan(),
+		},
+	}
 
-type genCmd struct {
-	*baseCmd
 }
 
-func newGenCmd() *genCmd {
-	cc := &genCmd{}
-	cc.baseCmd = newBaseCmd(&cobra.Command{
-		Use:   "gen",
-		Short: "A collection of several useful generators.",
-	})
+type genCommand struct {
+	rootCmd *rootCommand
 
-	cc.cmd.AddCommand(
-		newGenDocCmd().getCommand(),
-		newGenManCmd().getCommand(),
-		createGenDocsHelper().getCommand(),
-		createGenChromaStyles().getCommand())
-
-	return cc
+	commands []simplecobra.Commander
+}
+
+func (c *genCommand) Commands() []simplecobra.Commander {
+	return c.commands
+}
+
+func (c *genCommand) Name() string {
+	return "gen"
+}
+
+func (c *genCommand) Run(ctx context.Context, cd *simplecobra.Commandeer, args []string) error {
+	return nil
+}
+
+func (c *genCommand) WithCobraCommand(cmd *cobra.Command) error {
+	cmd.Short = "A collection of several useful generators."
+	return nil
+}
+
+func (c *genCommand) Init(cd, runner *simplecobra.Commandeer) error {
+	c.rootCmd = cd.Root.Command.(*rootCommand)
+	return nil
 }