log maxuid bumping less aggressively

we can bump the internal variable whereever convenient, but we cannot
log it until we know that all messages were copied, as otherwise we
could miss some new messages after an interruption. with the new
approach, interruption would merely cause some additonal traffic.

src/sync.c

@@ -1224,6 +1224,12 @@ box_loaded( int sts, void *aux )
 						Fprintf( svars->jfp, "+ %d %d\n", srec->uid[M], srec->uid[S] );
 						debug( "  -> pair(%d,%d) created\n", srec->uid[M], srec->uid[S] );
 					}
+					if (svars->maxuid[1-t] < tmsg->uid) {
+						/* We do this here for simplicity. However, logging must be delayed until
+						 * all messages were propagated, as skipped messages could otherwise be
+						 * logged before the propagation of messages with lower UIDs completes. */
+						svars->maxuid[1-t] = tmsg->uid;
+					}
 					if ((tmsg->flags & F_FLAGGED) || tmsg->size <= svars->chan->stores[t]->max_size) {
 						if (tmsg->flags) {
 							srec->flags = tmsg->flags;
@@ -1502,10 +1508,6 @@ msg_copied_p2( sync_vars_t *svars, sync_rec_t *srec, int t, message_t *tmsg, int
 	}
 	if (!tmsg->srec) {
 		tmsg->srec = srec;
-		if (svars->maxuid[1-t] < tmsg->uid) {
-			svars->maxuid[1-t] = tmsg->uid;
-			Fprintf( svars->jfp, "%c %d\n", ")("[t], tmsg->uid );
-		}
 	}
 }
 
@@ -1519,6 +1521,8 @@ msgs_copied( sync_vars_t *svars, int t )
 	if (!(svars->state[t] & ST_SENT_NEW) || svars->new_done[t] < svars->new_total[t])
 		return;
 
+	Fprintf( svars->jfp, "%c %d\n", ")("[t], svars->maxuid[1-t] );
+
 	if (svars->state[t] & ST_FIND_NEW) {
 		debug( "finding just copied messages on %s\n", str_ms[t] );
 		svars->drv[t]->find_new_msgs( svars->ctx[t], msgs_found_new, AUX );