httpd: fix several bugs triggering by realtive path in -h DIR.

function                                             old     new   delta
handle_incoming_and_exit                            2657    2659      +2
send_cgi_and_exit                                    869     862      -7
parse_conf                                          1647    1626     -21
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 2/-28)             Total: -26 bytes

1 files changed, 5 insertions, 3 deletions

diff --git a/libbb/concat_path_file.c b/libbb/concat_path_file.c
index 9aae601a4..dd6909fc2 100644
--- a/libbb/concat_path_file.c
+++ b/libbb/concat_path_file.c
@@ -8,9 +8,11 @@
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
 
-/* concatenate path and file name to new allocation buffer,
- * not adding '/' if path name already has '/'
-*/
+/* Concatenate path and filename to new allocated buffer.
+ * Add '/' only as needed (no duplicate // are produced).
+ * If path is NULL, it is assumed to be "/".
+ * filename should not be NULL.
+ */
 
 #include "libbb.h"