lei: use RENAME_NOREPLACE on Linux 3.15+

One syscall is better than two for atomicity in Maildirs.  This
means there's no window where another process can see both the
old and new file at the same time (link && unlink), nor a window
where we might inadvertantly clobber an existing file if we were
to do `stat && rename'.

1 files changed, 1 insertions, 0 deletions

diff --git a/MANIFEST b/MANIFEST
index af1522d7..9fd979ef 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -528,6 +528,7 @@ t/psgi_v2.t
 t/purge.t
 t/qspawn.t
 t/reindex-time-range.t
+t/rename_noreplace.t
 t/replace.t
 t/reply.t
 t/run.perl