add utils for adding/removing tags

anki/facts.py

@@ -117,6 +117,18 @@ insert or replace into facts values (?, ?, ?, ?, ?, ?, ?, ?, ?)""",
     def stringTags(self):
         return canonifyTags(self.tags)
 
+    def delTag(self, tag):
+        rem = []
+        for t in self.tags:
+            if t.lower() == tag.lower():
+                rem.append(t)
+        for r in rem:
+            self.tags.remove(r)
+
+    def addTag(self, tag):
+        # duplicates will be stripped on save
+        self.tags.append(tag)
+
     # Unique/duplicate checks
     ##################################################
 

anki/sched.py

@@ -537,7 +537,7 @@ queue = 2 %s and due <= :lim order by %s limit %d""" % (
             (card.lapses-lf) % (max(lf/2, 1)) == 0):
             # add a leech tag
             f = card.fact()
-            f.tags.append("leech")
+            f.addTag("leech")
             f.flush()
             # handle
             if conf['leechAction'][0] == 0: