Re: [found the culprit]

[Uwe Brauer]

   > It seems I misunderstood your original report: you wanted Z on a .tgz
   > file to only uncompress it?  

Yes! Either Z or any other letter or combination.

   > That indeed has been changed in Emacs 26, for consistency with a
   > .tar.gz file. I don't think it's a good idea to have the previous
   > subtle difference back.

   > I do think that Z on a compressed Tar archive, be it a .tar.gz or
   > .tgz file, should not by default unpack the archive. We could have
   > a special prefix arg to request that, and by default we should just
   > uncompress the file. But that's a different issue.

So I am confused now. What is you personal preference?

  Z: tgz (tar.gz)--> tar

Or 

 Z: tgz (tar.gz)--> unpack

I would prefer to have both actions, say   

Z: tgz (tar.gz)--> tar and 
prefix+Z  tgz (tar.gz)--> unpack

Or the other way around.

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