lib: add public accessor for database from query

This is to make it easier for clients of the library to update to the
new error code returning versions of notmuch_query_search_messages

lib/Makefile.local

@@ -11,7 +11,7 @@ LIBNOTMUCH_VERSION_MAJOR = 4
 # the time of release for any additions to the library interface,
 # (and when it is incremented, the release version of the library should
 #  be reset to 0).
-LIBNOTMUCH_VERSION_MINOR = 2
+LIBNOTMUCH_VERSION_MINOR = 3
 
 # The release version the library interface. This should be incremented at
 # the time of release if there have been no changes to the interface, (but

lib/notmuch.h

@@ -712,6 +712,12 @@ typedef enum {
 const char *
 notmuch_query_get_query_string (notmuch_query_t *query);
 
+/**
+ * Return the notmuch database of this query. See notmuch_query_create.
+ */
+notmuch_database_t *
+notmuch_query_get_database (notmuch_query_t *query);
+
 /**
  * Exclude values for notmuch_query_set_omit_excluded. The strange
  * order is to maintain backward compatibility: the old FALSE/TRUE

lib/query.cc

@@ -654,3 +654,9 @@ notmuch_query_count_threads (notmuch_query_t *query)
 
     return count;
 }
+
+notmuch_database_t *
+notmuch_query_get_database (notmuch_query_t *query)
+{
+    return query->notmuch;
+}