guix: lint: Add checker for new upstream versions.

* guix/scripts/lint.scm (check-for-updates): New procedure.
(%checkers): Add it.
* guix/scripts/refresh.scm (importer-modules, %updaters): Move
from here ...
* guix/upstream.scm: ... to here.

guix/scripts/lint.scm

@@ -33,6 +33,7 @@
   #:use-module (guix licenses)
   #:use-module (guix records)
   #:use-module (guix ui)
+  #:use-module (guix upstream)
   #:use-module (guix utils)
   #:use-module (guix memoization)
   #:use-module (guix scripts)
@@ -73,6 +74,7 @@
             check-mirror-url
             check-license
             check-vulnerabilities
+            check-for-updates
             check-formatting
             run-checkers
 
@@ -826,6 +828,17 @@ from ~s: ~a (~s)~%")
                                  (string-join (map vulnerability-id unpatched)
                                               ", ")))))))))
 
+(define (check-for-updates package)
+  "Check if there is an update available for PACKAGE."
+  (match (package-latest-release* package (force %updaters))
+    ((? upstream-source? source)
+     (when (version>? (upstream-source-version source)
+                      (package-version package))
+       (emit-warning package
+                     (format #f (G_ "can be upgraded to ~a~%")
+                             (upstream-source-version source)))))
+    (#f #f))) ; cannot find newer upstream release
+
 
 ;;;
 ;;; Source code formatting.
@@ -991,6 +1004,10 @@ or a list thereof")
      (description "Check the Common Vulnerabilities and Exposures\
  (CVE) database")
      (check       check-vulnerabilities))
+   (lint-checker
+     (name        'refresh)
+     (description "Check the package for new upstream releases")
+     (check       check-for-updates))
    (lint-checker
      (name        'formatting)
      (description "Look for formatting issues in the source")

guix/scripts/refresh.scm

@@ -30,7 +30,6 @@
   #:use-module (guix packages)
   #:use-module (guix profiles)
   #:use-module (guix upstream)
-  #:use-module (guix discovery)
   #:use-module (guix graph)
   #:use-module (guix scripts graph)
   #:use-module (guix monads)
@@ -46,8 +45,7 @@
   #:use-module (srfi srfi-26)
   #:use-module (srfi srfi-37)
   #:use-module (ice-9 binary-ports)
-  #:export (guix-refresh
-            %updaters))
+  #:export (guix-refresh))
 
 
 ;;;
@@ -162,22 +160,6 @@ specified with `--select'.\n"))
 ;;; Updates.
 ;;;
 
-(define (importer-modules)
-  "Return the list of importer modules."
-  (cons (resolve-interface '(guix gnu-maintenance))
-        (all-modules (map (lambda (entry)
-                            `(,entry . "guix/import"))
-                          %load-path))))
-
-(define %updaters
-  ;; The list of publically-known updaters.
-  (delay (fold-module-public-variables (lambda (obj result)
-                                         (if (upstream-updater? obj)
-                                             (cons obj result)
-                                             result))
-                                       '()
-                                       (importer-modules))))
-
 (define (lookup-updater-by-name name)
   "Return the updater called NAME."
   (or (find (lambda (updater)

guix/upstream.scm

@@ -20,6 +20,7 @@
 (define-module (guix upstream)
   #:use-module (guix records)
   #:use-module (guix utils)
+  #:use-module (guix discovery)
   #:use-module ((guix download)
                 #:select (download-to-store))
   #:use-module (guix gnupg)
@@ -55,6 +56,7 @@
             upstream-updater-predicate
             upstream-updater-latest
 
+            %updaters
             lookup-updater
 
             download-tarball
@@ -146,6 +148,22 @@ correspond to the same version."
   (pred        upstream-updater-predicate)
   (latest      upstream-updater-latest))
 
+(define (importer-modules)
+  "Return the list of importer modules."
+  (cons (resolve-interface '(guix gnu-maintenance))
+        (all-modules (map (lambda (entry)
+                            `(,entry . "guix/import"))
+                          %load-path))))
+
+(define %updaters
+  ;; The list of publically-known updaters.
+  (delay (fold-module-public-variables (lambda (obj result)
+                                         (if (upstream-updater? obj)
+                                             (cons obj result)
+                                             result))
+                                       '()
+                                       (importer-modules))))
+
 (define (lookup-updater package updaters)
   "Return an updater among UPDATERS that matches PACKAGE, or #f if none of
 them matches."