Tweak the startup message to be more helpful

Instead of just saying "boogity boogity!" let's actually warn people
that they need to configure stuff right to be safe, and point them
at instructions for how to do that.

Resolves bug 2474.

changes/bug2474

@@ -0,0 +1,5 @@
+  o Minor features
+    - Try to make the introductory warning message that Tor prints on
+      startup more useful for actually finding help and information.
+      Resolves bug2474.
+

src/or/main.c

@@ -1886,9 +1886,19 @@ tor_init(int argc, char *argv[])
       add_temp_log(LOG_NOTICE);
   }
 
-  log(LOG_NOTICE, LD_GENERAL, "Tor v%s. This is experimental software. "
-      "Do not rely on it for strong anonymity. (Running on %s)",get_version(),
-      get_uname());
+  {
+    const char *version = get_version();
+    log_notice(LD_GENERAL, "Tor v%s running on %s.", version, get_uname());
+
+    log_notice(LD_GENERAL, "WARNING: Tor can't help you if you use it wrong. "
+               "Learn how to be safe at "
+               "https://www.torproject.org/download/download#warning");
+
+    if (strstr(version, "alpha"))
+      log_notice(LD_GENERAL, "This is an alpha release; do not rely on it for "
+                 "strong anonymity.");
+  }
+
 
   if (network_init()<0) {
     log_err(LD_BUG,"Error initializing network; exiting.");