Tune AppConfigDir and docs for Storage module

caddy.go

@@ -61,11 +61,10 @@ type Config struct {
 	Logging *Logging     `json:"logging,omitempty"`
 
 	// StorageRaw is a storage module that defines how/where Caddy
-	// stores assets (such as TLS certificates). By default, this is
-	// the local file system (`caddy.storage.file_system` module).
-	// If the `XDG_DATA_HOME` environment variable is set, then
-	// `$XDG_DATA_HOME/caddy` is the default folder. Otherwise,
-	// `$HOME/.local/share/caddy` is the default folder.
+	// stores assets (such as TLS certificates). The default storage
+	// module is `caddy.storage.file_system` (the local file system),
+	// and the default path
+	// [depends on the OS and environment](/docs/conventions#data-directory).
 	StorageRaw json.RawMessage `json:"storage,omitempty" caddy:"namespace=caddy.storage inline_key=module"`
 
 	// AppsRaw are the apps that Caddy will load and run. The

storage.go

@@ -84,14 +84,13 @@ func homeDirUnsafe() string {
 //
 // Ref: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
 func AppConfigDir() string {
-	basedir := os.Getenv("XDG_CONFIG_HOME")
-	if basedir == "" {
-		var err error
-		basedir, err = os.UserConfigDir()
-		if err != nil {
-			Log().Warn("unable to determine directory for user configuration; falling back to current directory", zap.Error(err))
-			return "./caddy"
-		}
+	if basedir := os.Getenv("XDG_CONFIG_HOME"); basedir != "" {
+		return filepath.Join(basedir, "caddy")
+	}
+	basedir, err := os.UserConfigDir()
+	if err != nil {
+		Log().Warn("unable to determine directory for user configuration; falling back to current directory", zap.Error(err))
+		return "./caddy"
 	}
 	subdir := "caddy"
 	switch runtime.GOOS {