[Patch v2 3/3] lib: fix an exclude bug

[Mark Walters <markwalters1009@gmail.com>]

When the exclude tags contain a tag that does not occur anywhere in
the Xapian database the exclusion fails. We modify the way the query
is constructed to `work around' this. (In fact the new code is cleaner
anyway.)

It also seems to fix another exclusion failure bug reported by
jrollins but we have not yet worked out why it helps in that case.
---
 lib/query.cc |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/query.cc b/lib/query.cc
index ab18fbc..2b73d72 100644
--- a/lib/query.cc
+++ b/lib/query.cc
@@ -213,13 +213,14 @@ notmuch_query_search_messages (notmuch_query_t *query)
 
 	if (query->exclude_terms) {
 	    exclude_query = _notmuch_exclude_tags (query, final_query);
-	    exclude_query = Xapian::Query (Xapian::Query::OP_AND,
-					   exclude_query, final_query);
 
 	    if (query->omit_excluded_messages)
 		final_query = Xapian::Query (Xapian::Query::OP_AND_NOT,
 					     final_query, exclude_query);
 	    else {
+		exclude_query = Xapian::Query (Xapian::Query::OP_AND,
+					   exclude_query, final_query);
+
 		enquire.set_weighting_scheme (Xapian::BoolWeight());
 		enquire.set_query (exclude_query);
 
-- 
1.7.9.1