Re: master 6d6bf46 2/2: Make dired-do-compress work for *.tar.gz files

[Paul Eggert]

On 10/14/2015 12:58 AM, Oleh Krehel wrote:
> > Also, not every 'tar' has the -z option.  Emacs should use -z only
> > >after it's verified that the installed 'tar' supports -z.
> How can this be determined?

Pare the output of "tar --help".  For an example, see how 
progmodes/grep.el checks for the --color option of grep.