Add hack to allow cleaner command line opts

joern-cli/frontends/javasrc2cpg/src/main/scala/io/joern/javasrc2cpg/JavaSrc2Cpg.scala

@@ -56,8 +56,8 @@ object JavaSrc2Cpg {
       JavaSrcEnvVar.values.foreach { envVar =>
         val currentValue = Option(System.getenv(envVar.name)).getOrElse("<unset>")
         println(s"${envVar.name}:")
-        println(s"- Description  : ${envVar.description}")
-        println(s"- Current value: $currentValue")
+        println(s"  Description  : ${envVar.description}")
+        println(s"  Current value: $currentValue")
       }
   }
 

joern-cli/frontends/javasrc2cpg/src/main/scala/io/joern/javasrc2cpg/Main.scala

@@ -92,16 +92,23 @@ private object Frontend {
         .text("JDK used for resolving builtin Java types. If not set, current classpath will be used"),
       opt[Unit]("show-env")
         .action((_, c) => c.withShowEnv(true))
-        // This should really be a print-and-exit but, with the current scopt setup, input paths
-        // are still required, so for now `javasrc2cpg --show-env <inputs>` is less confusing
-        // than `javasrc2cpg --show-env <dummy input to keep scopt happy>`
-        .text("print information about environment variables used by javasrc2cpg prior to analysis")
+        .text("print information about environment variables used by javasrc2cpg prior to analysis and exit.")
     )
   }
 }
 
 object Main extends X2CpgMain(cmdLineParser, new JavaSrc2Cpg()) {
 
+  override def main(args: Array[String]): Unit = {
+    // TODO: This is a hack to allow users to use the "--show-env" option without having
+    //  to specify an input argument. Clean this up when adding this option to more frontends.
+    if (args.contains("--show-env")) {
+      super.main(Array("--show-env", "<input_dir_placeholder>"))
+    } else {
+      super.main(args)
+    }
+  }
+
   def run(config: Config, javasrc2Cpg: JavaSrc2Cpg): Unit = {
     if (config.showEnv) {
       JavaSrc2Cpg.showEnv()