guix: scripts: Parse $GUIX_BUILD_OPTIONS separately.

Appending to "raw" args broke optional parameters in 'guix package -I'
and 'guix package -A', and possibly other places.  Therefore, switch to
parsing each set of options on its own and append resulting alists
together afterwards.

* guix/scripts/archive.scm (parse-options-from): Rename from
  (parse-options) and add explicit argument.  New form of (parse-options)
  using its old algorithm via -from function.
* guix/scripts/build.scm: Ditto.
* guix/scripts/environment.scm: Ditto.
* guix/scripts/package.scm: Ditto.
* guix/scripts/system.scm: Ditto.
* tests/guix-package.sh: Add test.
* doc/guix.texi (Invoking guix build): Make it clear that the options
  are parsed independently.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index f2a25dd65a..56228601cc 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -477,8 +477,12 @@ Build the operating system declared in FILE according to ACTION.\n"))
 (define (guix-system . args)
   (define (parse-options)
     ;; Return the alist of option values.
-    (args-fold* (append args (environment-build-options))
-                %options
+    (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)