lib: Remove the notion of TAGS_INVALID

This rather ugly hack was recently obviated by the removal of the
notmuch_database_set_maildir_sync function. Now, clients must make
explicit calls to do any syncrhonization between maildir flags and
tags. So the library no longer needs to worry about doing inconsistent
synchronization while a message is only partially added.

lib/database.cc

@@ -1642,13 +1642,6 @@ notmuch_database_add_message (notmuch_database_t *notmuch,
 
 	_notmuch_message_add_filename (message, filename);
 
-	/* This is a new message or it has a new filename and as such,
-	 * its tags in database either do not exists or might be out
-	 * of date. We assign the tags later in notmuch new, but until
-	 * then we should not synchronize the tags back to the maildir
-	 * flags (if notmuch is configured to do so). */
-	notmuch_message_set_flag(message, NOTMUCH_MESSAGE_FLAG_TAGS_INVALID, TRUE);
-
 	/* Is this a newly created message object? */
 	if (private_status == NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND) {
 	    _notmuch_message_add_term (message, "type", "mail");

lib/message.cc

@@ -882,9 +882,6 @@ notmuch_message_maildir_flags_to_tags (notmuch_message_t *message)
     }
     status = notmuch_message_thaw (message);
 
-    /* From now on, we can synchronize the tags from the database to
-     * the mailstore. */
-    notmuch_message_set_flag (message, NOTMUCH_MESSAGE_FLAG_TAGS_INVALID, FALSE);
     return status;
 }
 

lib/notmuch.h

@@ -779,8 +779,7 @@ notmuch_message_get_filename (notmuch_message_t *message);
 
 /* Message flags */
 typedef enum _notmuch_message_flag {
-    NOTMUCH_MESSAGE_FLAG_MATCH,
-    NOTMUCH_MESSAGE_FLAG_TAGS_INVALID,
+    NOTMUCH_MESSAGE_FLAG_MATCH
 } notmuch_message_flag_t;
 
 /* Get a value of a flag for the email corresponding to 'message'. */