Merge branch 'maint'

* maint:
  Prepare for 1.6.1.4.
  Make repack less likely to corrupt repository
  fast-export: ensure we traverse commits in topological order
  Clear the delta base cache if a pack is rebuilt

Conflicts:
	RelNotes

sha1_file.c

@@ -689,6 +689,7 @@ void free_pack_by_name(const char *pack_name)
 	while (*pp) {
 		p = *pp;
 		if (strcmp(pack_name, p->pack_name) == 0) {
+			clear_delta_base_cache();
 			close_pack_windows(p);
 			if (p->pack_fd != -1)
 				close(p->pack_fd);