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

2 files changed, 9 insertions, 4 deletions

diff --git a/tpl/data/data_test.go b/tpl/data/data_test.go
index bcdddc9f4..9b21dc8aa 100644
--- a/tpl/data/data_test.go
+++ b/tpl/data/data_test.go
@@ -21,7 +21,6 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/spf13/viper"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -29,7 +28,7 @@ import (
 func TestGetCSV(t *testing.T) {
 	t.Parallel()
 
-	ns := New(newDeps(viper.New()))
+	ns := newTestNs()
 
 	for i, test := range []struct {
 		sep     string
@@ -123,7 +122,7 @@ func TestGetCSV(t *testing.T) {
 func TestGetJSON(t *testing.T) {
 	t.Parallel()
 
-	ns := New(newDeps(viper.New()))
+	ns := newTestNs()
 
 	for i, test := range []struct {
 		url     string
diff --git a/tpl/data/resources_test.go b/tpl/data/resources_test.go
index f0b027955..79e9b3907 100644
--- a/tpl/data/resources_test.go
+++ b/tpl/data/resources_test.go
@@ -127,7 +127,7 @@ func TestScpGetRemote(t *testing.T) {
 func TestScpGetRemoteParallel(t *testing.T) {
 	t.Parallel()
 
-	ns := New(newDeps(viper.New()))
+	ns := newTestNs()
 
 	content := []byte(`T€st Content 123`)
 	srv, cl := getTestServer(func(w http.ResponseWriter, r *http.Request) {
@@ -176,3 +176,9 @@ func newDeps(cfg config.Provider) *deps.Deps {
 		ContentSpec: cs,
 	}
 }
+
+func newTestNs() *Namespace {
+	v := viper.New()
+	v.Set("contentDir", "content")
+	return New(newDeps(v))
+}