import: utils: Add API to peek procedure bodies.

* guix/import/utils.scm (peekable-lambda, peek-body): Add procedures.
* .dir-locals.el: Add peekable-lambda indentation.

Signed-off-by: Liliana Marie Prikler <liliana.prikler@gmail.com>

guix/import/utils.scm

@@ -14,6 +14,7 @@
 ;;; Copyright © 2022 Kyle Meyer <kyle@kyleam.com>
 ;;; Copyright © 2022 Philip McGrath <philip@philipmcgrath.com>
 ;;; Copyright © 2025 Cayetano Santos <csantosb@inventati.org>
+;;; Copyright © 2025 Nicolas Graves <ngraves@ngraves.fr>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -66,6 +67,9 @@
             url-fetch
             guix-hash-url
 
+            peekable-lambda
+            peek-body
+
             package-names->package-inputs
             maybe-inputs
             maybe-native-inputs
@@ -165,6 +169,14 @@ thrown."
   "Return the hash of FILENAME in nix-base32 format."
   (bytevector->nix-base32-string (file-sha256 filename)))
 
+(define-syntax-rule (peekable-lambda args this-body)
+  (lambda args
+    #((body . this-body))
+    this-body))
+
+(define (peek-body proc)
+  (procedure-property proc 'body))
+
 (define %spdx-license-identifiers
   ;; https://spdx.org/licenses/
   ;; The gfl1.0, nmap, repoze