store: Add 'query-path-info*'.

* guix/scripts/size.scm (query-path-info*): Move to...
* guix/store.scm (query-path-info*): ... here.

guix/scripts/size.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -53,15 +53,6 @@
 (define substitutable-path-info*
   (store-lift substitutable-path-info))
 
-(define (query-path-info* item)
-  "Monadic version of 'query-path-info' that returns #f when ITEM is not in
-the store."
-  (lambda (store)
-    (guard (c ((nix-protocol-error? c)
-               ;; ITEM is not in the store; return #f.
-               (values #f store)))
-      (values (query-path-info store item) store))))
-
 (define (file-size item)
   "Return the size in bytes of ITEM, resorting to information from substitutes
 if ITEM is not in the store."

guix/store.scm

@@ -107,6 +107,7 @@
             references
             references/substitutes
             references*
+            query-path-info*
             requisites
             referrers
             optimize-store
@@ -1398,6 +1399,15 @@ where FILE is the entry's absolute file name and STAT is the result of
 (define references*
   (store-lift references))
 
+(define (query-path-info* item)
+  "Monadic version of 'query-path-info' that returns #f when ITEM is not in
+the store."
+  (lambda (store)
+    (guard (c ((nix-protocol-error? c)
+               ;; ITEM is not in the store; return #f.
+               (values #f store)))
+      (values (query-path-info store item) store))))
+
 (define-inlinable (current-system)
   ;; Consult the %CURRENT-SYSTEM fluid at bind time.  This is equivalent to
   ;; (lift0 %current-system %store-monad), but inlinable, thus avoiding