add rel='nofollow' to external links

lib/default.php

@@ -317,7 +317,8 @@ $default =
         'nofollow' =>
         array('subscribers' => true,
               'members' => true,
-              'peopletag' => true),
+              'peopletag' => true,
+              'external' => 'always'), // Options: 'sometimes', 'never', default = 'always'
         'http' => // HTTP client settings when contacting other sites
         array('ssl_cafile' => false, // To enable SSL cert validation, point to a CA bundle (eg '/usr/lib/ssl/certs/ca-certificates.crt')
               'curl' => false, // Use CURL backend for HTTP fetches if available. (If not, PHP's socket streams will be used.)

lib/util.php

@@ -145,7 +145,6 @@ function common_switch_locale($language=null)
     textdomain("statusnet");
 }
 
-
 function common_timezone()
 {
     if (common_logged_in()) {
@@ -860,7 +859,8 @@ function common_linkify($url) {
             $longurl = $url;
         }
     }
-    $attrs = array('href' => $canon, 'title' => $longurl, 'rel' => 'external');
+
+    $attrs = array('href' => $canon, 'title' => $longurl);
 
     $is_attachment = false;
     $attachment_id = null;
@@ -896,6 +896,16 @@ function common_linkify($url) {
         $attrs['id'] = "attachment-{$attachment_id}";
     }
 
+    // Whether to nofollow
+
+    $nf = common_config('nofollow', 'external');
+
+    if ($nf == 'never') {
+        $attrs['rel'] = 'external';
+    } else {
+        $attrs['rel'] = 'nofollow external';
+    }
+
     return XMLStringer::estring('a', $attrs, $url);
 }