Ignore new special field _r_met

COUCHDB-2655
diff --git a/src/couch_doc.erl b/src/couch_doc.erl
index 6fc9b09..39fe4f3 100644
--- a/src/couch_doc.erl
+++ b/src/couch_doc.erl
@@ -86,6 +86,8 @@
             [{<<"_conflicts">>, revs_to_strs(Conflicts)}];
         ({deleted_conflicts, DConflicts}) ->
             [{<<"_deleted_conflicts">>, revs_to_strs(DConflicts)}];
+        ({r_met, Bool}) ->
+            [{<<"_r_met">>, Bool}];
         (_) ->
             []
         end, Meta).
@@ -193,6 +195,11 @@
     % we already got the rev from the _revisions
     transfer_fields(Rest,Doc);
 
+transfer_fields([{<<"_r_met">>, _Bool} | Rest], Doc) ->
+    % _r_met is informational only and has no bearing on
+    % how we'll use the document.
+    transfer_fields(Rest,Doc);
+
 transfer_fields([{<<"_attachments">>, {JsonBins}} | Rest], Doc) ->
     Atts = [couch_att:from_json(Name, Props) || {Name, {Props}} <- JsonBins],
     transfer_fields(Rest, Doc#doc{atts=Atts});