(ido-enable-prefix): Improve previous doc fix.

[gnu-emacs] / lisp / env.el

diff --git a/lisp/env.el b/lisp/env.el
index 81760ececfc57d125e17b59c3326825ee30d95e8..5a3de0ac71235548a37312d1fd530d51a94516b9 100644 (file)
--- a/lisp/env.el
+++ b/lisp/env.el
@@ -90,38 +90,39 @@ Use `$$' to insert a single dollar sign."
 
 ;; Fixme: Should `process-environment' be recoded if LC_CTYPE &c is set?
 
-(defun setenv (variable &optional value unset substitute-env-vars)
+(defun setenv (variable &optional value substitute-env-vars)
   "Set the value of the environment variable named VARIABLE to VALUE.
 VARIABLE should be a string.  VALUE is optional; if not provided or
-nil, the environment variable VARIABLE will be removed.  UNSET
-if non-nil means to remove VARIABLE from the environment.
-SUBSTITUTE-ENV-VARS, if non-nil, means to substitute environment
-variables in VALUE with `substitute-env-vars', where see.
-Value is the new value if VARIABLE, or nil if removed from the
-environment.
+nil, the environment variable VARIABLE will be removed.
 
 Interactively, a prefix argument means to unset the variable.
 Interactively, the current value (if any) of the variable
 appears at the front of the history list when you type in the new value.
 Interactively, always replace environment variables in the new value.
 
+SUBSTITUTE-ENV-VARS, if non-nil, means to substitute environment
+variables in VALUE with `substitute-env-vars', which see.
+This is normally used only for interactive calls.
+
+The return value is the new value of VARIABLE, or nil if
+it was removed from the environment.
+
 This function works by modifying `process-environment'.
 
 As a special case, setting variable `TZ' calls `set-time-zone-rule' as
 a side-effect."
   (interactive
    (if current-prefix-arg
-       (list (read-envvar-name "Clear environment variable: " 'exact) nil t)
+       (list (read-envvar-name "Clear environment variable: " 'exact) nil)
      (let* ((var (read-envvar-name "Set environment variable: " nil))
            (value (getenv var)))
        (when value
-        (push value setenv-history))
+        (add-to-history 'setenv-history value))
        ;; Here finally we specify the args to give call setenv with.
        (list var
             (read-from-minibuffer (format "Set %s to value: " var)
                                   nil nil nil 'setenv-history
                                   value)
-            nil
             t))))
   (if (and (multibyte-string-p variable) locale-coding-system)
       (let ((codings (find-coding-systems-string (concat variable value))))
@@ -129,10 +130,9 @@ a side-effect."
                    (memq (coding-system-base locale-coding-system) codings))
          (error "Can't encode `%s=%s' with `locale-coding-system'"
                 variable (or value "")))))
-  (if unset
-      (setq value nil)
-    (if substitute-env-vars
-       (setq value (substitute-env-vars value))))
+  (and value
+       substitute-env-vars
+       (setq value (substitute-env-vars value)))
   (if (multibyte-string-p variable)
       (setq variable (encode-coding-string variable locale-coding-system)))
   (if (and value (multibyte-string-p value))