(Fexpand_file_name): Doc fix.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/fileio.c b/src/fileio.c
index cf3ec5bc44f..0208b9c618a 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -819,7 +819,13 @@ note that these simplifications are done without checking the resulting
 file names in the file system.
 An initial `~/' expands to your home directory.
 An initial `~USER/' expands to USER's home directory.
-See also the function `substitute-in-file-name'.  */)
+See also the function `substitute-in-file-name'.
+
+For technical reasons, this function can return correct but
+non-intuitive results for the root directory; for instance,
+\(expand-file-name ".." "/") returns "/..".  For this reason, use
+(directory-file-name (file-name-directory dirname)) to traverse a
+filesystem tree, not (expand-file-name ".."  dirname).  */)
      (name, default_directory)
      Lisp_Object name, default_directory;
 {