ui: Deduplicate 'show-what-to-build*'.

* guix/ui.scm (show-what-to-build*): New procedure.
* guix/scripts/environment.scm (show-what-to-build*): Delete.
* guix/scripts/system.scm (show-what-to-build*): Likewise.
* build-aux/make-binary-tarball.scm (show-what-to-build*): Likewise.

build-aux/make-binary-tarball.scm

@@ -27,9 +27,6 @@
              (gnu system install)
              (ice-9 match))
 
-(define show-what-to-build*
-  (store-lift show-what-to-build))
-
 (define copy-file*
   (lift2 copy-file %store-monad))
 

guix/scripts/environment.scm

@@ -192,9 +192,6 @@ packages."
    (append-map transitive-inputs packages)))
 
 ;; TODO: Deduplicate these.
-(define show-what-to-build*
-  (store-lift show-what-to-build))
-
 (define set-build-options-from-command-line*
   (store-lift set-build-options-from-command-line))
 

guix/scripts/system.scm

@@ -67,8 +67,6 @@
   (store-lift references))
 (define topologically-sorted*
   (store-lift topologically-sorted))
-(define show-what-to-build*
-  (store-lift show-what-to-build))
 
 
 (define* (copy-item item target

guix/ui.scm

@@ -57,6 +57,7 @@
             string->number*
             size->number
             show-what-to-build
+            show-what-to-build*
             show-manifest-transaction
             call-with-error-handling
             with-error-handling
@@ -453,6 +454,9 @@ available for download."
                   (null? download) download)))
     (pair? build)))
 
+(define show-what-to-build*
+  (store-lift show-what-to-build))
+
 (define (right-arrow port)
   "Return either a string containing the 'RIGHT ARROW' character, or an ASCII
 replacement if PORT is not Unicode-capable."