hugolib: Enable override of theme base template only

This commit fixes the base template lookup order to match the behaviour of regular templates.

```
1. <current-path>/<template-name>-baseof.<suffix>, e.g. list-baseof.<suffix>.
2. <current-path>/baseof.<suffix>
3. _default/<template-name>-baseof.<suffix>, e.g. list-baseof.<suffix>.
4. _default/baseof.<suffix>

For each of the steps above, it will first look in the project, then, if theme is set,
in the theme's layouts folder.
```

Fixes #2783

1 files changed, 15 insertions, 0 deletions

diff --git a/helpers/path.go b/helpers/path.go
index 6a35a55ca..7dea0b0dd 100644
--- a/helpers/path.go
+++ b/helpers/path.go
@@ -157,6 +157,12 @@ func AbsPathify(inPath string) string {
 	return filepath.Clean(filepath.Join(viper.GetString("workingDir"), inPath))
 }
 
+// GetLayoutDirPath returns the absolute path to the layout file dir
+// for the current Hugo project.
+func GetLayoutDirPath() string {
+	return AbsPathify(viper.GetString("layoutDir"))
+}
+
 // GetStaticDirPath returns the absolute path to the static file dir
 // for the current Hugo project.
 func GetStaticDirPath() string {
@@ -172,6 +178,15 @@ func GetThemeDir() string {
 	return ""
 }
 
+// GetRelativeThemeDir gets the relative root directory of the current theme, if there is one.
+// If there is no theme, returns the empty string.
+func GetRelativeThemeDir() string {
+	if ThemeSet() {
+		return strings.TrimPrefix(filepath.Join(viper.GetString("themesDir"), viper.GetString("theme")), FilePathSeparator)
+	}
+	return ""
+}
+
 // GetThemeStaticDirPath returns the theme's static dir path if theme is set.
 // If theme is set and the static dir doesn't exist, an error is returned.
 func GetThemeStaticDirPath() (string, error) {