Preserve file mode (permissions) on tidy.

This changes the method of writing out the tidied file from ->spew() to
->append({truncate => 1}). spew() copies the new file into place, which ends
up resetting the file mode based on the current umask. Using append() instead
preserves the file permissions and ownership, without us having to keep track
of the mode and resetting it after writing the file.

lib/Code/TidyAll.pm

@@ -350,7 +350,10 @@ sub process_file {
 
         # write new contents out to disk
         $contents = $result->new_contents;
-        path( $full_path . $self->output_suffix )->spew($contents);
+
+        # We don't use ->spew because that creates a new file and renames it,
+        # losing the existing mode setting in the process.
+        path( $full_path . $self->output_suffix )->append( { truncate => 1 }, $contents );
 
         # change the in memory contents of the cache (but don't update yet)
         $cache_model->file_contents($contents) unless $self->output_suffix;

t/lib/Test/Code/TidyAll/Basic.pm

@@ -78,6 +78,20 @@ sub test_basic : Tests {
     );
 }
 
+sub test_filemode : Tests {
+    my $self     = shift;
+    my $root_dir = $self->create_dir( { "foo.txt" => "abc" } );
+    my $file     = $root_dir->child('foo.txt');
+    $file->chmod('0755');
+    my $ct = Code::TidyAll->new(
+        plugins  => { test_plugin('UpperText') => { select => '**/foo*' } },
+        root_dir => $root_dir,
+    );
+    $ct->process_paths($file);
+    is( $file->slurp,      "ABC" );
+    is( $file->stat->mode, 0100755 );
+}
+
 sub test_multiple_plugin_instances : Tests {
     my $self = shift;
     $self->tidy(