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, 9 insertions, 2 deletions

diff --git a/source/content_directory_test.go b/source/content_directory_test.go
index 9874acec2..ed00af625 100644
--- a/source/content_directory_test.go
+++ b/source/content_directory_test.go
@@ -17,11 +17,15 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/gohugoio/hugo/helpers"
+
 	"github.com/gohugoio/hugo/hugofs"
 	"github.com/spf13/viper"
+	"github.com/stretchr/testify/require"
 )
 
 func TestIgnoreDotFilesAndDirectories(t *testing.T) {
+	assert := require.New(t)
 
 	tests := []struct {
 		path                string
@@ -35,7 +39,6 @@ func TestIgnoreDotFilesAndDirectories(t *testing.T) {
 		{"foobar/.barfoo.md", true, nil},
 		{".barfoo.md", true, nil},
 		{".md", true, nil},
-		{"", true, nil},
 		{"foobar/barfoo.md~", true, nil},
 		{".foobar/barfoo.md~", true, nil},
 		{"foobar~/barfoo.md", false, nil},
@@ -51,9 +54,13 @@ func TestIgnoreDotFilesAndDirectories(t *testing.T) {
 	for i, test := range tests {
 
 		v := viper.New()
+		v.Set("contentDir", "content")
 		v.Set("ignoreFiles", test.ignoreFilesRegexpes)
+		fs := hugofs.NewMem(v)
+		ps, err := helpers.NewPathSpec(fs, v)
+		assert.NoError(err)
 
-		s := NewSourceSpec(v, hugofs.NewMem(v))
+		s := NewSourceSpec(ps, fs.Source)
 
 		if ignored := s.IgnoreFile(filepath.FromSlash(test.path)); test.ignore != ignored {
 			t.Errorf("[%d] File not ignored", i)