Make ForgeModDetectionRule more comprehensive

gradle.properties

@@ -7,5 +7,5 @@ org.gradle.configuration-cache=true
 # org.gradle.unsafe.isolated-projects=true
 
 group=net.msrandom
-version=0.5.9
+version=0.5.10
 kotlin.code.style=official

minecraft-codev-forge/src/main/kotlin/net/msrandom/minecraftcodev/forge/mappings/ForgeModDetectionRule.kt

@@ -4,11 +4,32 @@ import net.msrandom.minecraftcodev.forge.MinecraftCodevForgePlugin.Companion.FOR
 import net.msrandom.minecraftcodev.forge.MinecraftCodevForgePlugin.Companion.NEOFORGE_MODS_TOML
 import net.msrandom.minecraftcodev.remapper.ModDetectionRule
 import java.nio.file.FileSystem
+import java.util.jar.JarFile
+import java.util.jar.Manifest
 import kotlin.io.path.exists
+import kotlin.io.path.inputStream
+import kotlin.io.path.notExists
 
 class ForgeModDetectionRule : ModDetectionRule {
-    override fun invoke(fileSystem: FileSystem) =
-        fileSystem.getPath("META-INF", FORGE_MODS_TOML).exists() ||
-            fileSystem.getPath("META-INF", NEOFORGE_MODS_TOML).exists() ||
-            fileSystem.getPath("mcmod.info").exists()
+    override fun invoke(fileSystem: FileSystem): Boolean {
+        val hasMetadata = fileSystem.getPath("META-INF", FORGE_MODS_TOML).exists() ||
+                fileSystem.getPath("META-INF", NEOFORGE_MODS_TOML).exists() ||
+                fileSystem.getPath("mcmod.info").exists()
+
+        if (hasMetadata) {
+            return true
+        }
+
+        val manifestPath = fileSystem.getPath(JarFile.MANIFEST_NAME)
+
+        if (manifestPath.notExists()) {
+            return false
+        }
+
+        val manifest = manifestPath.inputStream().use(::Manifest)
+
+        return manifest.mainAttributes.keys.any {
+            "fml" in it.toString().lowercase() || "forge" in it.toString().lowercase()
+        }
+    }
 }