Fix exit codes:

- `--help`, `--version` etc should exit with `0` i.e. no error ("not enough args" case should still trigger an error)
- error reading config file should exit with `1`

Slightly refactor AppInitRPC/AppInitRawTx to return standard exit codes (EXIT_FAILURE/EXIT_SUCCESS) or CONTINUE_EXECUTION (-1)

src/bitcoin-tx.cpp

@@ -30,8 +30,13 @@ using namespace std;
 
 static bool fCreateBlank;
 static map<string,UniValue> registers;
+static const int CONTINUE_EXECUTION=-1;
 
-static bool AppInitRawTx(int argc, char* argv[])
+//
+// This function returns either one of EXIT_ codes when it's expected to stop the process or
+// CONTINUE_EXECUTION when it's expected to continue further.
+//
+static int AppInitRawTx(int argc, char* argv[])
 {
     //
     // Parameters
@@ -89,9 +94,13 @@ static bool AppInitRawTx(int argc, char* argv[])
         strUsage += HelpMessageOpt("set=NAME:JSON-STRING", _("Set register NAME to given JSON-STRING"));
         fprintf(stdout, "%s", strUsage.c_str());
 
-        return false;
+        if (argc < 2) {
+            fprintf(stderr, "Error: too few parameters\n");
+            return EXIT_FAILURE;
+        }
+        return EXIT_SUCCESS;
     }
-    return true;
+    return CONTINUE_EXECUTION;
 }
 
 static void RegisterSetJson(const string& key, const string& rawJson)
@@ -678,8 +687,9 @@ int main(int argc, char* argv[])
     SetupEnvironment();
 
     try {
-        if(!AppInitRawTx(argc, argv))
-            return EXIT_FAILURE;
+        int ret = AppInitRawTx(argc, argv);
+        if (ret != CONTINUE_EXECUTION)
+            return ret;
     }
     catch (const std::exception& e) {
         PrintExceptionContinue(&e, "AppInitRawTx()");