Separate out generator logic from the multisrc boilerplate itself

multisrc/src/main/java/generator/GeneratorMain.kt

@@ -0,0 +1,28 @@
+package generator
+
+import java.io.File
+
+/**
+ * Finds and calls all `ThemeSourceGenerator`s
+ */
+fun main(args: Array<String>) {
+    val userDir = System.getProperty("user.dir")!!
+    val sourcesDirPath = "$userDir/multisrc/src/main/java/eu/kanade/tachiyomi/multisrc"
+    val sourcesDir = File(sourcesDirPath)
+
+    // find all theme packages
+    sourcesDir.list()!!
+        .filter { File(sourcesDir, it).isDirectory }
+        .forEach { themeSource ->
+            // Find all XxxGenerator.kt files and invoke main from them
+            File("$sourcesDirPath/$themeSource").list()!!
+                .filter { it.endsWith("Generator.kt") }
+                .mapNotNull { generatorClass ->
+                    // Find Java class and extract method lists
+                    Class.forName("eu/kanade/tachiyomi/multisrc/$themeSource/$generatorClass".replace("/", ".").substringBefore(".kt"))
+                        .methods
+                        .find { it.name == "main" }
+                }
+                .forEach { it.invoke(null, emptyArray<String>()) }
+        }
+}