Suppress GNU tar warnings about unknown keywords

[maxhq]

If an archive is e.g. built on MacOS, usually additional informations are
included. When unpacking this using GNU tar there are messages like:

tar: Ignoring unknown extended header keyword `SCHILY.ino'
tar: Ignoring unknown extended header keyword `SCHILY.nlink'
tar: Ignoring unknown extended header keyword `SCHILY.dev'

To prevent this the option --warning=no-unknown-keyword was added if tar
is the GNU version (BSD tar does not support the option).

[skaji]

At least, tar (GNU tar) 1.15.1 does not support that option...

> docker run -i -t centos:centos5 bash -l
[root@c2755652684c /]# cat /etc/redhat-release
CentOS release 5.11 (Final)
[root@c2755652684c /]# tar --version
tar (GNU tar) 1.15.1
[root@c2755652684c /]# tar czf tmp.tar.gz tmp
[root@c2755652684c /]# ls -l tmp.tar.gz
-rw-r--r-- 1 root root 107 Jul 26 16:49 tmp.tar.gz
[root@c2755652684c /]# tar --warning=no-unknown-keyword -ztf tmp.tar.gz
tar: unrecognized option `--warning=no-unknown-keyword'
Try `tar --help' or `tar --usage' for more information.

[maxhq]

Thanks skaji for pointing that out!
The option was added on 2009-08-05 and thus released with tar 1.23.
I added a check for tar version 1.23 or newer using the version module.

[maxhq]

The TravisCI checks only fail for Perl 5.12 which seems quite strange to me. Could you please trigger a new check (can only be done with repo write access)?

[maxhq]

Thank you, now they all pass ;-)