guix-register: Perform deduplication even when --prefix is passed.

Fixes <http://bugs.gnu.org/19044>.

* nix/guix-register/guix-register.cc (register_validity): Change the (optimize
  && prefix.empty ()) condition to just (optimize).  Change settings.nixStore
  around the loop.  Prepend PREFIX to the argument passed to 'optimisePath'.
* tests/guix-register.sh: Use 'guix-register -p' with duplicate files, and
  make sure they are deduplicated on the target.  Adjust existing tests.

nix/guix-register/guix-register.cc

@@ -1,5 +1,5 @@
 /* GNU Guix --- Functional package management for GNU
-   Copyright (C) 2013, 2014 Ludovic Courtès <ludo@gnu.org>
+   Copyright (C) 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
    Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012,
      2013 Eelco Dolstra <eelco.dolstra@logicblox.com>
 
@@ -192,13 +192,21 @@ register_validity (LocalStore *store, std::istream &input,
      store's '.links' directory, which means 'optimisePath' would try to link
      to that instead of linking to the target store.  Thus, disable
      deduplication in this case.  */
-  if (optimize && prefix.empty ())
+  if (optimize)
     {
       /* Make sure deduplication is enabled.  */
       settings.autoOptimiseStore = true;
 
+      std::string store_dir = settings.nixStore;
+
+      /* 'optimisePath' creates temporary links under 'settings.nixStore' and
+	 this must be the real target store, under PREFIX, to avoid
+	 cross-device links.  Thus, temporarily switch the value of
+	 'settings.nixStore'.  */
+      settings.nixStore = prefix + store_dir;
       foreach (ValidPathInfos::const_iterator, i, infos)
-	store->optimisePath (i->path);
+	store->optimisePath (prefix + i->path);
+      settings.nixStore = store_dir;
     }
 }
 

tests/guix-register.sh

@@ -56,15 +56,14 @@ guile -c "
   (exit (= (stat:ino (stat \"$new_file\"))
            (stat:ino (stat \"$new_file2\"))))"
 
-# Make sure both are valid, and delete them.
+# Make sure both are valid.
 guile -c "
    (use-modules (guix store))
    (define s (open-connection))
    (exit (and (valid-path? s \"$new_file\")
               (valid-path? s \"$new_file2\")
               (null? (references s \"$new_file\"))
-              (null? (references s \"$new_file2\"))
+              (null? (references s \"$new_file2\"))))"
-              (pair? (delete-paths s (list \"$new_file\" \"$new_file2\")))))"
 
 
 #
@@ -98,6 +97,33 @@ guix-register --prefix "$new_store" "$closure"
 guix-register -p "$new_store" \
     --state-directory "$new_store/chbouib" "$closure"
 
+# Register duplicate files.
+cp "$new_file" "$new_file2" "$new_store_dir"
+guix-register -p "$new_store" <<EOF
+$new_file
+
+0
+EOF
+guix-register -p "$new_store" <<EOF
+$new_file2
+
+0
+EOF
+
+copied_duplicate1="$new_store_dir/`basename $new_file`"
+copied_duplicate2="$new_store_dir/`basename $new_file2`"
+
+# Make sure there is indeed deduplication under $new_store and that there are
+# no cross-store hard links.
+guile -c "
+  (exit (and (= (stat:ino (stat \"$copied_duplicate1\"))
+                (stat:ino (stat \"$copied_duplicate2\")))
+             (not (= (stat:ino (stat \"$new_file\"))
+                     (stat:ino (stat \"$copied_duplicate1\"))))))"
+
+# Delete them.
+guix gc -d "$new_file" "$new_file2"
+
 # Now make sure this is recognized as valid.
 
 ls -R "$new_store"
@@ -131,9 +157,12 @@ do
     # that name in a 'valid-path?' query because 'assertStorePath' would kill
     # us because of the wrong prefix.  So we just list dead paths instead.
     guile -c "
-      (use-modules (guix store))
+      (use-modules (guix store) (srfi srfi-1))
       (define s (open-connection \"$GUIX_DAEMON_SOCKET\"))
-      (exit (equal? (list \"$copied\") (dead-paths s)))"
+      (exit (lset= string=?
+                   (pk 1 (list \"$copied\" \"$copied_duplicate1\"
+                               \"$copied_duplicate2\"))
+                   (pk 2 (dead-paths s))))"
 
     # Kill the daemon so we can access the database below (otherwise we may
     # get "database is locked" errors.)