all: Document the Output Formats feature

This commit also adds a new command, docshelper, with some utility funcs that adds a JSON datafiles to /docs/data that would be a pain to create and maintain by hand.

Fixes #3242

commands/gendocshelper.go

@@ -0,0 +1,70 @@
+// Copyright 2017-present 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.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package commands
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/spf13/cobra"
+	"github.com/spf13/hugo/docshelper"
+)
+
+type genDocsHelper struct {
+	target string
+	cmd    *cobra.Command
+}
+
+func createGenDocsHelper() *genDocsHelper {
+	g := &genDocsHelper{
+		cmd: &cobra.Command{
+			Use:    "docshelper",
+			Short:  "Generate some data files for the Hugo docs.",
+			Hidden: true,
+		},
+	}
+
+	g.cmd.RunE = func(cmd *cobra.Command, args []string) error {
+		return g.generate()
+	}
+
+	g.cmd.PersistentFlags().StringVarP(&g.target, "dir", "", "docs/data", "Data dir")
+
+	return g
+}
+
+func (g *genDocsHelper) generate() error {
+	fmt.Println("Generate docs data to", g.target)
+
+	targetFile := filepath.Join(g.target, "docs.json")
+
+	f, err := os.Create(targetFile)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	enc := json.NewEncoder(f)
+	enc.SetIndent("", "  ")
+
+	if err := enc.Encode(docshelper.DocProviders); err != nil {
+		return err
+	}
+
+	fmt.Println("Done!")
+	return nil
+
+}

commands/hugo.go

@@ -197,6 +197,7 @@ func AddCommands() {
 	genCmd.AddCommand(genautocompleteCmd)
 	genCmd.AddCommand(gendocCmd)
 	genCmd.AddCommand(genmanCmd)
+	genCmd.AddCommand(createGenDocsHelper().cmd)
 }
 
 // initHugoBuilderFlags initializes all common flags, typically used by the