Added comma-delimited string attrib type

internal/codegen/codegen.go

@@ -39,6 +39,16 @@ func simpleTemplate(paramType, convertExpr string) string {
 	`, paramType, conversion)
 }
 
+func listTemplate(separator string) string {
+	return fmt.Sprintf(`func %%s(value ...string) hatmill.Attrib {
+		return hatmill.Attrib{
+			Key: "%%s",
+			Value: strings.Join(value, "%s"),
+		}
+	}
+	`, separator)
+}
+
 var attribTypes = map[string]AttribTypeInfo{
 	"string": {Template: simpleTemplate("string", "%s")},
 	"bool": {
@@ -62,14 +72,12 @@ var attribTypes = map[string]AttribTypeInfo{
 		Imports:  []string{"strconv"},
 	},
 	"space list": {
-		Template: `func %s(value ...string) hatmill.Attrib {
-			return hatmill.Attrib{
-				Key: "%s",
-				Value: strings.Join(value, " "),
-			}
-		}
-		`,
-		Imports: []string{"strings"},
+		Template: listTemplate(" "),
+		Imports:  []string{"strings"},
+	},
+	"comma list": {
+		Template: listTemplate(","),
+		Imports:  []string{"strings"},
 	},
 }