05/10: guix system: Make 'init' idempotent again.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository guix.

commit f3f1d0a5578b4ad6d85494283eedfaa62b28fe2c
Author: Ludovic Courtès <address@hidden>
Date:   Tue Jul 3 11:24:32 2018 +0200

    guix system: Make 'init' idempotent again.
    
    This fixes a regression introduced in
    df2f6400b1fbc282ef4d6dd7124ea1c17adc23c2: since the new
    'register-path' (actually 'reset-timestamps') would make files
    read-only, 'delete-file-recursively' would fail to delete them.  Thus,
    re-running 'guix system init' on an already-populated store would fail
    with a 'delete-file' EPERM.
    
    * guix/scripts/system.scm (copy-item): Use 'lstat' instead of
    'file-exists?'.  Call 'make-file-writable' on each directory below
    DEST.
---
 guix/scripts/system.scm | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index 92e9223..69bd05b 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -126,7 +126,11 @@ REFERENCES as its set of references."
     ;; Remove DEST if it exists to make sure that (1) we do not fail badly
     ;; while trying to overwrite it (see <http://bugs.gnu.org/20722>), and
     ;; (2) we end up with the right contents.
-    (when (file-exists? dest)
+    (when (false-if-exception (lstat dest))
+      (for-each make-file-writable
+                (find-files dest (lambda (file stat)
+                                   (eq? 'directory (stat:type stat)))
+                            #:directories? #t))
       (delete-file-recursively dest))
 
     (copy-recursively item dest