database: Reset timestamps to one second after the Epoch.

Previously, store items registered in the database by this code (for
instance, store items retrieved by 'guix offload' and passed to
'restore-file-set') would have an mtime of 0 instead of 1.

This would cause problems for things like .go files: Guile would
consider them to be older than the corresponding .scm file, and
consequently it would ignore them and possibly use another (incorrect)
.go file.

Reported by Ricardo Wurmus.

* guix/store/database.scm (reset-timestamps): Pass 1, not 0, to
'utime'.
* tests/store-database.scm ("register-path"): Check the mtime of FILE
and REF.

guix/store/database.scm

@@ -190,12 +190,14 @@ Every store item in REFERENCES must already be registered."
 (define (reset-timestamps file)
   "Reset the modification time on FILE and on all the files it contains, if
 it's a directory.  While at it, canonicalize file permissions."
+  ;; Note: We're resetting to one second after the Epoch like 'guix-daemon'
+  ;; has always done.
   (let loop ((file file)
              (type (stat:type (lstat file))))
     (case type
       ((directory)
        (chmod file #o555)
-       (utime file 0 0 0 0)
+       (utime file 1 1 0 0)
        (let ((parent file))
          (for-each (match-lambda
                      (("." . _) #f)
@@ -209,10 +211,10 @@ it's a directory.  While at it, canonicalize file permissions."
                                 (type type))))))
                    (scandir* parent))))
       ((symlink)
-       (utime file 0 0 0 0 AT_SYMLINK_NOFOLLOW))
+       (utime file 1 1 0 0 AT_SYMLINK_NOFOLLOW))
       (else
        (chmod file (if (executable-file? file) #o555 #o444))
-       (utime file 0 0 0 0)))))
+       (utime file 1 1 0 0)))))
 
 (define* (register-path path
                         #:key (references '()) deriver prefix

tests/store-database.scm

@@ -32,7 +32,8 @@
 
 (test-begin "store-database")
 
-(test-assert "register-path"
+(test-equal "register-path"
+  '(1 1)
   (let ((file (string-append (%store-prefix) "/" (make-string 32 #\f)
                              "-fake")))
     (when (valid-path? %store file)
@@ -50,7 +51,9 @@
       (and (valid-path? %store file)
            (equal? (references %store file) (list ref))
            (null? (valid-derivers %store file))
-           (null? (referrers %store file))))))
+           (null? (referrers %store file))
+           (list (stat:mtime (lstat file))
+                 (stat:mtime (lstat ref)))))))
 
 (test-equal "new database"
   (list 1 2)