Fix searching for message

The message search currently looks for an exact match, which is
pretty much never what anyone would want to do, and moreover,
does not match the gerrit documentation.  It should actually
perform a substring match, so switch to using "like %<message>%".

Change-Id: I281d59887de247eb3f3fd508635efa44714fa054

gertty/search/__init__.py

@@ -62,7 +62,7 @@ class SearchCompiler(object):
 if __name__ == '__main__':
     class Dummy(object):
         pass
-    query = 'ref:^refs/heads/foo.*'
+    query = 'message:"Blueprint"'
     lexer = tokenizer.SearchTokenizer()
     lexer.input(query)
     while True:

gertty/search/parser.py

@@ -224,7 +224,7 @@ def SearchParser():
         '''message_term : OP_MESSAGE string'''
         filters = []
         filters.append(gertty.db.revision_table.c.change_key == gertty.db.change_table.c.key)
-        filters.append(gertty.db.revision_table.c.message == p[2])
+        filters.append(gertty.db.revision_table.c.message.like('%%%s%%' % p[2]))
         s = select([gertty.db.change_table.c.key], correlate=False).where(and_(*filters))
         p[0] = gertty.db.change_table.c.key.in_(s)