lint: Check for trailing whitespace in description.

* guix/lint.scm (check-description-style): Check for trailing whitespace.
* tests/lint.scm: ("description: trailing whitespace"): New test.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

guix/lint.scm

@@ -300,6 +300,15 @@ by two spaces; possible infraction~p at ~{~a~^, ~}")
                                infractions)
                          #:field 'description)))))
 
+  (define (check-no-trailing-whitespace description)
+    "Check that DESCRIPTION doesn't have trailing whitespace."
+    (if (string-suffix? " " description)
+        (list
+         (make-warning package
+                       (G_ "description contains trailing whitespace")
+                       #:field 'description))
+        '()))
+
   (let ((description (package-description package)))
     (if (string? description)
         (append
@@ -309,6 +318,7 @@ by two spaces; possible infraction~p at ~{~a~^, ~}")
          ;; Use raw description for this because Texinfo rendering
          ;; automatically fixes end of sentence space.
          (check-end-of-sentence-space description)
+         (check-no-trailing-whitespace description)
          (match (check-texinfo-markup description)
            ((and warning (? lint-warning?)) (list warning))
            (plain-description

tests/lint.scm

@@ -160,6 +160,13 @@
                              (description "This is a 'quoted' thing."))))
      (check-description-style pkg))))
 
+(test-equal "description: trailing whitespace"
+  "description contains trailing whitespace"
+  (single-lint-warning-message
+   (let ((pkg (dummy-package "x"
+                              (description "Whitespace. "))))
+     (check-description-style pkg))))
+
 (test-equal "synopsis: not a string"
   "invalid synopsis: #f"
   (single-lint-warning-message