bug#19481: package.el: support .tar archives featuring a pax_global_header entry

[Eli Zaretskii <eliz@gnu.org>]

> From: Ivan Shmakov <ivan@siamics.net>
> Date: Sat, 31 Jan 2015 11:05:48 +0000
> 
>  >> * lisp/tar-mode.el (tar-header-extractable-p): New function.
>  >> (tar-untar-buffer): Use it; or use the value of the new optional
>  >> argument instead.
> 
>  >> * lisp/emacs-lisp/package.el (package-untar-buffer): Use
>  >> tar-header-extractable-p.
>  >> (package-tar-file-info): Consider the second file name in the
>  >> archive if the first one has no directory component.
> 
>  > Thanks.
> 
>  > Can we have a test suite for this file,
> 
> 	Which of the two?  (Or three, to count the .tar file produced by
> 	$ git archive.)

I meant tar-mode.el, and specifically where the new function is used.

> 	FTR, the two changes I suggest are not /inter/dependent, so I
> 	intend to push them as two separate commits.

Does the tar-header-extractable-p function make any sense without its
use in package.el?  If so, then yes, these should be 2 separate
commits.

>       (And I wonder if
> 	eit makes sense to now file a separate Severity: wishlist bug
> 	report for tar-header-extractable-p, so to provide a somewhat
> 	extended background for the feature.)

Not sure it's worth your while.

>  > Failing that, please describe how you tested these changes.
> 
> 	I’ve tested these using my MW package, like:
> 
> 	• C-x b *new-buffer* RET;
> 
> 	• M-x cd RET ~/devel/mw-el-2015/ RET;
> 
> 	• C-u M-! git archive --prefix=mw-0.2/ --format=tar
> 	  HEAD 2> /dev/null RET;
> 
> 	• M-x tar-mode RET;
> 
> 	• M-x package-install-from-buffer RET.

Did you try unpacking a "normal" tar archive, to see nothing is
broken?