Merge pull request #2 from Insprill/feature/loader-branch-validation

Validate loader branch syntax

Author: cam72cam

src/main/java/cam72cam/universalmodcore/Setup.java

@@ -23,7 +23,18 @@ public static void main(String[] args) throws IOException, GitAPIException {
                         Files.readAllBytes(Paths.get("umc.json"))
                 ))
         ).getAsJsonObject();
+
+        if (args.length == 0) {
+            System.err.println("No loader branch specified! Available branches can be found in the UniversalModCore GitHub repository.");
+            return;
+        }
         String loaderBranch = args[0];
+        String[] split = loaderBranch.split("-");
+        if (split.length < 2 || !split[0].matches("1\\.\\d*\\.\\d*") || !split[1].matches("[\\w-]+")) {
+            System.err.println("Invalid loader branch! It should be in the format '<minecraft-version>-<loader>'. For example, '1.12.2-forge'.");
+            return;
+        }
+
         Config config = new Config(configObj, loaderBranch);
 
         ZipInputStream zip = new ZipInputStream(config.openJarStream());