Changed the default value of --retry-wait to 0 for backward

compatibility.

Also updated usage doc.

doc/aria2c.1.asciidoc

@@ -204,7 +204,9 @@ aria2c -o myfile.zip "http://mirror1/file.zip" "http://mirror2/file.zip"
 
 [[aria2_optref_retry_wait]]*--retry-wait*=SEC::
 
-  Set the seconds to wait between retries. Default: '2'
+  Set the seconds to wait between retries. With SEC > 0, aria2 will
+  retry download when the HTTP server returns 503 response. Default:
+  '0'
 
 [[aria2_optref_server_stat_of]]*--server-stat-of*=FILE::
 

src/OptionHandlerFactory.cc

@@ -693,7 +693,7 @@ OptionHandlers OptionHandlerFactory::createOptionHandlers()
     SharedHandle<OptionHandler> op(new NumberOptionHandler
                                    (PREF_RETRY_WAIT,
                                     TEXT_RETRY_WAIT,
-                                    "2",
+                                    "0",
                                     0, 600));
     op->addTag(TAG_FTP);
     op->addTag(TAG_HTTP);

src/usage_text.h

@@ -59,7 +59,9 @@
     "                              Please note that in Metalink download, this\n" \
     "                              option has no effect and use -C option instead.")
 #define TEXT_RETRY_WAIT                                                 \
-  _(" --retry-wait=SEC             Set the seconds to wait between retries.")
+  _(" --retry-wait=SEC             Set the seconds to wait between retries. \n" \
+    "                              With SEC > 0, aria2 will retry download when the\n" \
+    "                              HTTP server returns 503 response.")
 #define TEXT_TIMEOUT                                            \
   _(" -t, --timeout=SEC            Set timeout in seconds.")
 #define TEXT_MAX_TRIES                                                  \