master ba918ec: Improve directory-append manual entry

[Lars Ingebrigtsen]

branch: master
commit ba918ecb7891c6d0bb7bbaab93b4316881166d94
Author: Lars Ingebrigtsen <larsi@gnus.org>
Commit: Lars Ingebrigtsen <larsi@gnus.org>

    Improve directory-append manual entry
    
    * doc/lispref/files.texi (Directory Names): Mention zero-length
    restriction.
---
 doc/lispref/files.texi | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/doc/lispref/files.texi b/doc/lispref/files.texi
index a624c2e..804cef2 100644
--- a/doc/lispref/files.texi
+++ b/doc/lispref/files.texi
@@ -2355,6 +2355,8 @@ didn't end with a slash.
 @end group
 @end example
 
+A zero-length directory or component is not allowed.
+
 This is almost the same as using @code{concat}, but @var{dirname} (and
 the non-final components) may or may not end with slash characters,
 and this function will not double those characters.