bug#40325: make backup files for "-i" option invisible

[nokangaroo]

The visible backup files create problems with file managers, e. g. they show up
in MATE, and I have to reload the folder to make them disappear. The following
patch creates invisible files:

--- sed/execute.c       2020-01-01 20:38:19.000000000 +0100
+++ sed/execute.c       2020-03-26 12:17:30.209662815 +0100
@@ -614,7 +614,7 @@
             }
         }
 
-      output_file.fp = ck_mkstemp (&input->out_file_name, tmpdir, "sed",
+      output_file.fp = ck_mkstemp (&input->out_file_name, tmpdir, ".sed",
                                    write_mode);
       register_cleanup_file (input->out_file_name);
       output_file.missing_newline = false;


This works because ck_mkstemp tests for strlen.
BTW why not use /tmp instead of '.'?

-- 
nokangaroo <address@hidden>