Modify module to make it GNU getopt compliant.

Add support for short options with embedded arguments (e.g. -j2).
Add support for implicit boolean options (e.g. -q -> {quiet, true}).
Add support for option terminator ("--").

examples/rebar_test.escript

@@ -16,7 +16,7 @@
 -author('juanjo@comellas.org').
 
 main([]) ->
-    getopt:usage(option_spec_list(), escript:script_name());
+    usage();
 main(Args) ->
     OptSpecList = option_spec_list(),
     io:format("For command line: ~p~n"
@@ -26,16 +26,25 @@ main(Args) ->
             io:format("Options:~n  ~p~n~nNon-option arguments:~n  ~p~n", [Options, NonOptArgs]);
         {error, {Reason, Data}} ->
             io:format("Error: ~s ~p~n~n", [Reason, Data]),
-            getopt:usage(OptSpecList, "ex1.escript")
+            usage(OptSpecList)
     end.
 
 
+usage() ->
+    usage(option_spec_list()).
+
+usage(OptSpecList) ->
+    getopt:usage(OptSpecList, escript:script_name(), "[var1=val1 ...] [command1 ...]",
+                 [{"var=value", "Variables that will affect the compilation (e.g. debug=1)"},
+                  {"command",   "Commands that will be executed by rebar (e.g. compile)"}]).
+
+
 option_spec_list() ->
+    CpuCount = erlang:system_info(logical_processors),
     [
      %% {Name,     ShortOpt,  LongOpt,       ArgSpec,               HelpMsg}
      {help,        $h,        "help",        undefined,             "Show the program options"},
-     {jobs,        $j,        "jobs",        {integer, 1},          "Number of concurrent jobs"},
+     {jobs,        $j,        "jobs",        {integer, CpuCount},   "Number of concurrent jobs"},
      {verbose,     $v,        "verbose",     {boolean, false},      "Be verbose about what gets done"},
-     {quiet,       $q,        "quiet",       {boolean, false},      "Be quiet about what gets done"},
      {force,       $f,        "force",       {boolean, false},      "Force"}
     ].