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, 22 insertions, 1 deletions

diff --git a/hugolib/testhelpers_test.go b/hugolib/testhelpers_test.go
index 6f513b3bf..5300eee22 100644
--- a/hugolib/testhelpers_test.go
+++ b/hugolib/testhelpers_test.go
@@ -51,6 +51,11 @@ type sitesBuilder struct {
 	// Default toml
 	configFormat string
 
+	// Default is empty.
+	// TODO(bep) revisit this and consider always setting it to something.
+	// Consider this in relation to using the BaseFs.PublishFs to all publishing.
+	workingDir string
+
 	// Base data/content
 	contentFilePairs  []string
 	templateFilePairs []string
@@ -83,6 +88,11 @@ func (s *sitesBuilder) Running() *sitesBuilder {
 	return s
 }
 
+func (s *sitesBuilder) WithWorkingDir(dir string) *sitesBuilder {
+	s.workingDir = dir
+	return s
+}
+
 func (s *sitesBuilder) WithConfigTemplate(data interface{}, format, configTemplate string) *sitesBuilder {
 	if format == "" {
 		format = "toml"
@@ -233,7 +243,17 @@ func (s *sitesBuilder) writeFilePairs(folder string, filenameContent []string) *
 	}
 	for i := 0; i < len(filenameContent); i += 2 {
 		filename, content := filenameContent[i], filenameContent[i+1]
-		writeSource(s.T, s.Fs, filepath.Join(folder, filename), content)
+		target := folder
+		// TODO(bep) clean  up this magic.
+		if strings.HasPrefix(filename, folder) {
+			target = ""
+		}
+
+		if s.workingDir != "" {
+			target = filepath.Join(s.workingDir, target)
+		}
+
+		writeSource(s.T, s.Fs, filepath.Join(target, filename), content)
 	}
 	return s
 }
@@ -458,6 +478,7 @@ func newTestDefaultPathSpec() *helpers.PathSpec {
 	v := viper.New()
 	// Easier to reason about in tests.
 	v.Set("disablePathToLower", true)
+	v.Set("contentDir", "content")
 	fs := hugofs.NewDefault(v)
 	ps, _ := helpers.NewPathSpec(fs, v)
 	return ps