ui: Factorize command-line + env. var. option parsing.

* guix/ui.scm (%default-argument-handler, parse-command-line): New
  procedures.
  (environment-build-options): Make private.
* guix/scripts/archive.scm (guix-archive)[parse-options,
  parse-options-from]: Remove.  Use 'parse-command-line' instead.
* guix/scripts/build.scm (guix-build): Likewise.
* guix/scripts/environment.scm (guix-environment): Likewise.
* guix/scripts/package.scm (guix-package): Likewise.
* guix/scripts/system.scm (guix-system): Likewise.
* tests/ui.scm (with-environment-variable): New macro.
  ("parse-command-line"): New test.

1 files changed, 4 insertions, 14 deletions

diff --git a/guix/scripts/environment.scm b/guix/scripts/environment.scm
index bb2ce53caf..c96ca351c4 100644
--- a/guix/scripts/environment.scm
+++ b/guix/scripts/environment.scm
@@ -217,22 +217,12 @@ packages."
 
 ;; Entry point.
 (define (guix-environment . args)
-  (define (parse-options)
-    ;; Return the alist of option values.
-    (append (parse-options-from args)
-            (parse-options-from (environment-build-options))))
-
-  (define (parse-options-from args)
-    ;; Actual parsing takes place here.
-    (args-fold* args %options
-                (lambda (opt name arg result)
-                  (leave (_ "~A: unrecognized option~%") name))
-                (lambda (arg result)
-                  (alist-cons 'package arg result))
-                %default-options))
+  (define (handle-argument arg result)
+    (alist-cons 'package arg result))
 
   (with-store store
-    (let* ((opts (parse-options))
+    (let* ((opts  (parse-command-line args %options (list %default-options)
+                                      #:argument-handler handle-argument))
            (pure? (assoc-ref opts 'pure))
            (command (assoc-ref opts 'exec))
            (inputs (packages->transitive-inputs