Add support for a content dir set per language

A sample config:

```toml
defaultContentLanguage = "en"
defaultContentLanguageInSubdir = true

[Languages]
[Languages.en]
weight = 10
title = "In English"
languageName = "English"
contentDir = "content/english"

[Languages.nn]
weight = 20
title = "På Norsk"
languageName = "Norsk"
contentDir = "content/norwegian"
```

The value of `contentDir` can be any valid path, even absolute path references. The only restriction is that the content dirs cannot overlap.

The content files will be assigned a language by

1. The placement: `content/norwegian/post/my-post.md` will be read as Norwegian content.
2. The filename: `content/english/post/my-post.nn.md` will be read as Norwegian even if it lives in the English content folder.

The content directories will be merged into a big virtual filesystem with one simple rule: The most specific language file will win.
This means that if both `content/norwegian/post/my-post.md` and `content/english/post/my-post.nn.md` exists, they will be considered duplicates and the version inside `content/norwegian` will win.

Note that translations will be automatically assigned by Hugo by the content file's relative placement, so `content/norwegian/post/my-post.md` will be a translation of `content/english/post/my-post.md`.

If this does not work for you, you can connect the translations together by setting a `translationKey` in the content files' front matter.

Fixes #4523
Fixes #4552
Fixes #4553

1 files changed, 15 insertions, 1 deletions

diff --git a/helpers/language.go b/helpers/language.go
index 49a25ccf7..731e9b088 100644
--- a/helpers/language.go
+++ b/helpers/language.go
@@ -41,6 +41,14 @@ type Language struct {
 	Title        string
 	Weight       int
 
+	Disabled bool
+
+	// If set per language, this tells Hugo that all content files without any
+	// language indicator (e.g. my-page.en.md) is in this language.
+	// This is usually a path relative to the working dir, but it can be an
+	// absolute directory referenece. It is what we get.
+	ContentDir string
+
 	Cfg config.Provider
 
 	// These are params declared in the [params] section of the language merged with the
@@ -66,7 +74,13 @@ func NewLanguage(lang string, cfg config.Provider) *Language {
 		params[k] = v
 	}
 	ToLowerMap(params)
-	l := &Language{Lang: lang, Cfg: cfg, params: params, settings: make(map[string]interface{})}
+
+	defaultContentDir := cfg.GetString("contentDir")
+	if defaultContentDir == "" {
+		panic("contentDir not set")
+	}
+
+	l := &Language{Lang: lang, ContentDir: defaultContentDir, Cfg: cfg, params: params, settings: make(map[string]interface{})}
 	return l
 }