Make Page an interface

The main motivation of this commit is to add a `page.Page` interface to replace the very file-oriented `hugolib.Page` struct.
This is all a preparation step for issue  #5074, "pages from other data sources".

But this also fixes a set of annoying limitations, especially related to custom output formats, and shortcodes.

Most notable changes:

* The inner content of shortcodes using the `{{%` as the outer-most delimiter will now be sent to the content renderer, e.g. Blackfriday.
  This means that any markdown will partake in the global ToC and footnote context etc.
* The Custom Output formats are now "fully virtualized". This removes many of the current limitations.
* The taxonomy list type now has a reference to the `Page` object.
  This improves the taxonomy template `.Title` situation and make common template constructs much simpler.

See #5074
Fixes #5763
Fixes #5758
Fixes #5090
Fixes #5204
Fixes #4695
Fixes #5607
Fixes #5707
Fixes #5719
Fixes #3113
Fixes #5706
Fixes #5767
Fixes #5723
Fixes #5769
Fixes #5770
Fixes #5771
Fixes #5759
Fixes #5776
Fixes #5777
Fixes #5778

config/configProvider.go

@@ -1,4 +1,4 @@
-// Copyright 2017-present The Hugo Authors. All rights reserved.
+// Copyright 2019 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.
@@ -40,3 +40,15 @@ func GetStringSlicePreserveString(cfg Provider, key string) []string {
 	}
 	return cast.ToStringSlice(sd)
 }
+
+// SetBaseTestDefaults provides some common config defaults used in tests.
+func SetBaseTestDefaults(cfg Provider) {
+	cfg.Set("resourceDir", "resources")
+	cfg.Set("contentDir", "content")
+	cfg.Set("dataDir", "data")
+	cfg.Set("i18nDir", "i18n")
+	cfg.Set("layoutDir", "layouts")
+	cfg.Set("assetDir", "assets")
+	cfg.Set("archetypeDir", "archetypes")
+	cfg.Set("publishDir", "public")
+}

config/services/servicesConfig.go

@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2019 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.
@@ -23,6 +23,7 @@ const (
 
 	disqusShortnameKey = "disqusshortname"
 	googleAnalyticsKey = "googleanalytics"
+	rssLimitKey        = "rssLimit"
 )
 
 // Config is a privacy configuration for all the relevant services in Hugo.
@@ -31,6 +32,7 @@ type Config struct {
 	GoogleAnalytics GoogleAnalytics
 	Instagram       Instagram
 	Twitter         Twitter
+	RSS             RSS
 }
 
 // Disqus holds the functional configuration settings related to the Disqus template.
@@ -61,6 +63,12 @@ type Twitter struct {
 	DisableInlineCSS bool
 }
 
+// RSS holds the functional configuration settings related to the RSS feeds.
+type RSS struct {
+	// Limit the number of pages.
+	Limit int
+}
+
 // DecodeConfig creates a services Config from a given Hugo configuration.
 func DecodeConfig(cfg config.Provider) (c Config, err error) {
 	m := cfg.GetStringMap(servicesConfigKey)
@@ -76,5 +84,9 @@ func DecodeConfig(cfg config.Provider) (c Config, err error) {
 		c.Disqus.Shortname = cfg.GetString(disqusShortnameKey)
 	}
 
+	if c.RSS.Limit == 0 {
+		c.RSS.Limit = cfg.GetInt(rssLimitKey)
+	}
+
 	return
 }

config/sitemap.go

@@ -0,0 +1,44 @@
+// Copyright 2019 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 config
+
+import (
+	"github.com/spf13/cast"
+	jww "github.com/spf13/jwalterweatherman"
+)
+
+// Sitemap configures the sitemap to be generated.
+type Sitemap struct {
+	ChangeFreq string
+	Priority   float64
+	Filename   string
+}
+
+func DecodeSitemap(prototype Sitemap, input map[string]interface{}) Sitemap {
+
+	for key, value := range input {
+		switch key {
+		case "changefreq":
+			prototype.ChangeFreq = cast.ToString(value)
+		case "priority":
+			prototype.Priority = cast.ToFloat64(value)
+		case "filename":
+			prototype.Filename = cast.ToString(value)
+		default:
+			jww.WARN.Printf("Unknown Sitemap field: %s\n", key)
+		}
+	}
+
+	return prototype
+}