Avoid marking files as attachments that are not locally uploaded, unless they're really oembedable. HTML-y things now excluded properly.

classes/File.php

@@ -352,6 +352,9 @@ class File extends Memcached_DataObject
                 $mimetype = substr($mimetype,0,$semicolon);
             }
             if(in_array($mimetype,$notEnclosureMimeTypes)){
+                // Never treat HTML as an enclosure type!
+                return false;
+            } else {
                 $oembed = File_oembed::staticGet('file_id',$this->id);
                 if($oembed){
                     $mimetype = strtolower($oembed->mimetype);

lib/util.php

@@ -877,7 +877,7 @@ function common_linkify($url) {
     }
 
     if (!empty($f)) {
-        if ($f->getEnclosure() || File_oembed::staticGet('file_id',$f->id)) {
+        if ($f->getEnclosure()) {
             $is_attachment = true;
             $attachment_id = $f->id;