Improve documentation of 'read-command'

* src/minibuf.c (Fread_command): Document the return value
when DEFAULT-VALUE is nil and the user enters nothing.
* doc/lispref/minibuf.texi (High-Level Completion): Document
the printed representation of a symbol whose name is empty.
(Bug#3522)

1 files changed, 2 insertions, 1 deletions

diff --git a/src/minibuf.c b/src/minibuf.c
index 6964f350ffe..a33ddf40a1c 100644
--- a/src/minibuf.c
+++ b/src/minibuf.c
@@ -1054,7 +1054,8 @@ the current input method and the setting of`enable-multibyte-characters'.  */)
 DEFUN ("read-command", Fread_command, Sread_command, 1, 2, 0,
        doc: /* Read the name of a command and return as a symbol.
 Prompt with PROMPT.  By default, return DEFAULT-VALUE or its first element
-if it is a list.  */)
+if it is a list.  If DEFAULT-VALUE is omitted or nil, and the user enters
+null input, return a symbol whose name is an empty string.  */)
   (Lisp_Object prompt, Lisp_Object default_value)
 {
   Lisp_Object name, default_string;