lint: archival: Trigger “Save Code Now” for VCSes other than Git.

Until now, ‘save-origin’ would be called only when given a
<git-reference>.  With this change, ‘save-origin’ gets called for other
version control systems as well.

* guix/lint.scm (swh-response->warning): New procedure, formerly in
‘check-archival’.
(vcs-origin, save-package-source): New procedures.
(check-archival)[response->warning]: Remove.
Call ‘save-package-source’ in both the Git and the non-Git cases.
* tests/lint.scm ("archival: missing svn revision"): New test.

Change-Id: I535e4ec89488faf83bfa544d5e4935fa73ef54fb

tests/lint.scm

@@ -1407,6 +1407,26 @@
                        (check-archival (dummy-package "x" (source origin)))))))
     (warning-contains? "scheduled" warnings)))
 
+(test-assert "archival: missing svn revision"
+  (let* ((origin   (origin
+                     (method svn-fetch)
+                     (uri (svn-reference
+                           (url "http://example.org/svn/foo")
+                           (revision "1234")))
+                     (sha256 (make-bytevector 32))))
+         ;; https://archive.softwareheritage.org/api/1/origin/save/
+         (save     "{ \"origin_url\": \"http://example.org/svn/foo\",
+                      \"save_request_date\": \"2014-11-17T22:09:38+01:00\",
+                      \"save_request_status\": \"accepted\",
+                      \"save_task_status\": \"scheduled\" }")
+         (warnings (with-http-server `((404 "No extid.") ;lookup-directory-by-nar-hash
+                                       (404 "No revision.") ;lookup-revision
+                                       (404 "No origin.")   ;lookup-origin
+                                       (200 ,save))         ;save-origin
+                     (parameterize ((%swh-base-url (%local-url)))
+                       (check-archival (dummy-package "x" (source origin)))))))
+    (warning-contains? "scheduled" warnings)))
+
 (test-equal "archival: revision available"
   '()
   (let* ((origin   (origin