This option makes tar sort the entries of directories that will be
added to an archive according to ORDER (none, name, or order).
Based on proposition by Dick Streefland (https://savannah.gnu.org/patch/?7892).
* src/common.h (savedir_sort_order): New global.
* src/create.c: Pass savedir_sort_order to streamsavedir.
* src/misc.c: Likewise.
* src/tar.c: New option --sort.
* NEWS: Update.
* doc/tar.texi: Document the --sort option.
* doc/tar.1: Likewise.
Make sure the changes become visible with --show-transformed-names.
* src/common.h (strip_compression_suffix): New function.
(one_top_level): Rename to one_top_level_dir. All uses changed.
* src/extract.c (extr_init): Use strip_compression_suffix.
Bail out if unable to determine top-level directory.
(maybe_prepend_name): Remove. All uses removed.
* src/tar.c (options): --one-top-level takes optional argument.
(parse_opt): Handle it.
* src/list.c (enforce_one_top_level): New function.
(transform_stat_info): Call enforce_one_top_level if required.
* src/suffix.c (compression_suffixes): List "tar" (no compression);
terminate with NULL entry.
(find_compression_suffix): New static.
(strip_compression_suffix): New function.
* doc/tar.1: Update.
* doc/tar.texi: Update.
* tests/onetop01.at: New testcase.
* tests/onetop02.at: New testcase.
* tests/onetop03.at: New testcase.
* tests/Makefile.am: Add new testcases.
* tests/testsuite.at: Likewise.
