Fix handling of old packwiz.json files with negative murmur2 values

src/main/kotlin/link/infra/packwiz/installer/Main.kt

@@ -101,7 +101,7 @@ class Main(args: Array<String>) {
 			cmd.getOptionValue("multimc-folder")?.let{ PackwizFilePath(it.toPath()) } ?: PackwizFilePath("..".toPath())
 		}
 		val manifestFile = ui.wrap("Invalid manifest file path") {
-			packFolder / (cmd.getOptionValue("meta-file") ?: "manifest.json")
+			packFolder / (cmd.getOptionValue("meta-file") ?: "packwiz.json")
 		}
 
 		// Start update process!

src/main/kotlin/link/infra/packwiz/installer/metadata/hash/Hash.kt

@@ -21,7 +21,14 @@ data class Hash<T>(val type: HashFormat<T>, val value: T) {
 
 		object UInt: Encoding<kotlin.UInt> {
 			override fun encodeToString(value: kotlin.UInt) = value.toString()
-			override fun decodeFromString(str: String) = str.toUInt()
+			override fun decodeFromString(str: String) =
+				try {
+					str.toUInt()
+				} catch (e: NumberFormatException) {
+					// Old packwiz.json values are signed; if they are negative they should be parsed as signed integers
+					// and reinterpreted as unsigned integers
+					str.toInt().toUInt()
+				}
 		}
 	}