python: Add binding for notmuch_query_add_tag_exclude

Implemented as the method `exclude_tag` of the class `Query`. This method takes
one argument, a string containing the name of the tag to exclude.

NEWS

@@ -22,6 +22,11 @@ from the config file.  Use something like:
       ...
     },
 
+Python Bindings
+---------------
+
+Add support for `notmuch_query_add_tag_exclude`
+
 Notmuch 0.18.1 (2014-06-25)
 ===========================
 

bindings/python/docs/source/query.rst

@@ -32,6 +32,8 @@
       :attr:`Query.SORT`) if explicitely specified via
       :meth:`set_sort`. By default it is set to `None`.
 
+   .. automethod:: exclude_tag
+
    .. automethod:: search_threads
 
    .. automethod:: search_messages

bindings/python/notmuch/query.py

@@ -118,6 +118,21 @@ class Query(object):
         self.sort = sort
         self._set_sort(self._query, sort)
 
+    _exclude_tag = nmlib.notmuch_query_add_tag_exclude
+    _exclude_tag.argtypes = [NotmuchQueryP, c_char_p]
+    _exclude_tag.resttype = None
+
+    def exclude_tag(self, tagname):
+        """Add a tag that will be excluded from the query results by default.
+
+        This exclusion will be overridden if this tag appears explicitly in the
+        query.
+
+        :param tagname: Name of the tag to be excluded
+        """
+        self._assert_query_is_initialized()
+        self._exclude_tag(self._query, _str(tagname))
+
     """notmuch_query_search_threads"""
     _search_threads = nmlib.notmuch_query_search_threads
     _search_threads.argtypes = [NotmuchQueryP]