Make HHVM's command line parsing closer to Zend

This diff makes some tweaks to how HHVM handles command line arguments
to match what Zend PHP does. This change will allow developers to type
"hhvm foo.php -x" at the command line and "-x" will get passed as an
argument to the PHP application as it would for Zend PHP.

The basic idea is that we detect the first occurrence of either "--" or a
non-option argument. If we encounter "--" first, all subsequent arguments
are passed along to the PHP application (though the "--" token itself gets
swallowed). If we encounter a non-option argument first, that argument
and everything after it are passed along to the PHP application.

hphp/runtime/base/program_functions.cpp

@@ -786,8 +786,8 @@ static void close_server_log_file(int kind) {
   }
 }
 
-static int execute_program_impl(int argc, char **argv) {
-  string usage = "Usage:\n\n\t";
+static int execute_program_impl(int argc, char** argv) {
+  string usage = "Usage:\n\n   ";
   usage += argv[0];
   usage += " [-m <mode>] [<options>] [<arg1>] [<arg2>] ...\n\nOptions";
 
@@ -858,8 +858,67 @@ static int execute_program_impl(int argc, char **argv) {
   p.add("arg", -1);
   variables_map vm;
   try {
-    store(command_line_parser(argc, argv).options(desc).positional(p).run(),
-          vm);
+    // We use the boost command line parser to do the initial parsing,
+    // and then we do a manual pass to find the first occurrence of
+    // either "--" or a non-option argument so that we can properly
+    // determine which arguments should be consumed by HHVM and which
+    // arguments should be passed to the PHP application.
+    //
+    // We instruct the boost command line parser to allow unrecognized
+    // options and we manually deal with raising an error when there is
+    // an unrecognized option; we need to do this because otherwise the
+    // boost parser may choke on arguments intended for PHP application.
+    // Also, during the manual pass we keep track of our position in the
+    // original argv array so that we can correctly detect the first
+    // occurrence of "--" (since the boost parser swallows this token).
+    auto opts = command_line_parser(argc, argv)
+      .options(desc)
+      .positional(p)
+      .allow_unregistered()
+      .run();
+    // argvPos will track where we are in the original argv array
+    int argvPos = 1;
+    for (unsigned i = 0; i < opts.options.size(); ++i) {
+      const auto& option = opts.options[i];
+      if (option.unregistered) {
+        Logger::Error("Error in command line: unknown option %s",
+                      option.original_tokens[0].c_str());
+        cout << desc << "n";
+        return -1;
+      }
+      // Check if we've encountered "--" and make sure that argvPos
+      // accounts for it
+      bool foundDashDash = !strcmp(argv[argvPos], "--");
+      if (foundDashDash) {
+        ++argvPos;
+      }
+      // If we haven't encountered "--" or the first non-option
+      // argument, update argvPos appropriately and keep scanning
+      if (!foundDashDash && option.position_key == -1) {
+        argvPos += option.original_tokens.size();
+        continue;
+      }
+      // We've found the first occurrence of "--" or a non-option
+      // argument. Truncate opts.options, and then take all the
+      // remaining arguments from the original argv array and insert
+      // them into opts.options.
+      opts.options.resize(i);
+      std::vector<basic_option<char> > vec;
+      int pos = 0;
+      for (int m = argvPos; m < argc; ++m) {
+        string str = argv[m];
+        basic_option<char> bo;
+        bo.string_key = "arg";
+        bo.position_key = pos++;
+        bo.value.push_back(str);
+        bo.original_tokens.push_back(str);
+        bo.unregistered = false;
+        bo.case_insensitive = false;
+        opts.options.push_back(bo);
+      }
+      break;
+    }
+    store(opts, vm);
     notify(vm);
     if (po.mode == "d") po.mode = "debug";
     if (po.mode == "s") po.mode = "server";