tag-util: do not reset list in parse_tag_command_line

The 'insert' command will be better served if parse_tag_command_line
modifies a pre-populated list (of new.tags) instead of clobbering the
list outright.  The sole existing caller, notmuch_tag_command, is
unaffected by this change.

tag-util.c

@@ -165,8 +165,6 @@ parse_tag_command_line (void *ctx, int argc, char **argv,
 
     int i;
 
-    tag_op_list_reset (tag_ops);
-
     for (i = 0; i < argc; i++) {
 	if (strcmp (argv[i], "--") == 0) {
 	    i++;

tag-util.h

@@ -81,6 +81,8 @@ parse_tag_line (void *ctx, char *line,
  * Output Parameters:
  *	ops	contains a list of tag operations
  *	query_str the search terms.
+ *
+ * The ops argument is not cleared.
  */
 
 tag_parse_status_t