bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Mike Kupfer]

The 26.1.90 NEWS file has this (new) entry for Dired:

  *** The 'Z' command on a directory name compresses all of its files.
  It produces a compressed '.tar.gz' archive with all the files in the
  directory and all of its subdirectories.  For symmetry, 'Z' on a
  '.tar.gz' or a '.tgz' archive extracts all the archived files into a
  directory whose name is the archive name sans the '.tar.gz' or '.tgz'
  extension.  (This change was actually made in Emacs 26.1, but was not
  called out in its NEWS.)

The description of the unpacking case implies that the user will see the
described behavior for any .tar.gz or .tgz file.  In reality, 'Z' simply
unpacks the archive.  The described behavior only happens if the archive
is structured in a canonical way, e.g., if 'Z' was used to create the
.tar.gz file.

The wording should be changed, so as not to mislead the user about what
'Z' does.  A user who misunderstands what 'Z' does could lose data due
to unanticipated overwrite when the archive is unpacked.  (Note that the
docstring for dired-do-compress says nothing about creating or unpacking
archive files.)

Also, and less important, I got the impression from the discussion on
emacs-devel that this feature was partially introduced in Emacs 25.
Wasn't the change in 26.1 just to make .tar.gz and .tgz behave the same?
I'm not sure it's worth trying to be that precise in the NEWS entry, but
I thought I'd mention it.

regards,
mike

In GNU Emacs 26.1.90 (build 1, x86_64-pc-linux-gnu, X toolkit, Xaw scroll bars)
 of 2018-11-19 built on alto
Windowing system distributor 'The X.Org Foundation', version 11.0.11902000
System Description:	Debian GNU/Linux 9.6 (stretch)

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bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Eli Zaretskii]

> From: Mike Kupfer <mkupfer@alum.berkeley.edu>
> Date: Tue, 20 Nov 2018 19:39:05 -0800
> 
> The 26.1.90 NEWS file has this (new) entry for Dired:
> 
>   *** The 'Z' command on a directory name compresses all of its files.
>   It produces a compressed '.tar.gz' archive with all the files in the
>   directory and all of its subdirectories.  For symmetry, 'Z' on a
>   '.tar.gz' or a '.tgz' archive extracts all the archived files into a
>   directory whose name is the archive name sans the '.tar.gz' or '.tgz'
>   extension.  (This change was actually made in Emacs 26.1, but was not
>   called out in its NEWS.)
> 
> The description of the unpacking case implies that the user will see the
> described behavior for any .tar.gz or .tgz file.  In reality, 'Z' simply
> unpacks the archive.  The described behavior only happens if the archive
> is structured in a canonical way, e.g., if 'Z' was used to create the
> .tar.gz file.
> 
> The wording should be changed, so as not to mislead the user about what
> 'Z' does.  A user who misunderstands what 'Z' does could lose data due
> to unanticipated overwrite when the archive is unpacked.  (Note that the
> docstring for dired-do-compress says nothing about creating or unpacking
> archive files.)

I don't think I understand.  Are you alluding to the case when the
archive includes absolute file names, or file names that raise above
the directory where the archive lives?  Or do you have some other case
in mind?

> Also, and less important, I got the impression from the discussion on
> emacs-devel that this feature was partially introduced in Emacs 25.
> Wasn't the change in 26.1 just to make .tar.gz and .tgz behave the same?
> I'm not sure it's worth trying to be that precise in the NEWS entry, but
> I thought I'd mention it.

You mean, say that some of the feature was available since Emacs 25?
I don't think it's important, no.

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Mike Kupfer]

Eli Zaretskii wrote:

> > The 26.1.90 NEWS file has this (new) entry for Dired:
> > 
> >   *** The 'Z' command on a directory name compresses all of its files.
> >   It produces a compressed '.tar.gz' archive with all the files in the
> >   directory and all of its subdirectories.  For symmetry, 'Z' on a
> >   '.tar.gz' or a '.tgz' archive extracts all the archived files into a
> >   directory whose name is the archive name sans the '.tar.gz' or '.tgz'
> >   extension.  (This change was actually made in Emacs 26.1, but was not
> >   called out in its NEWS.)
> > 
> > The description of the unpacking case implies that the user will see the
> > described behavior for any .tar.gz or .tgz file.  In reality, 'Z' simply
> > unpacks the archive.  The described behavior only happens if the archive
> > is structured in a canonical way, e.g., if 'Z' was used to create the
> > .tar.gz file.
> > 
> > The wording should be changed, so as not to mislead the user about what
> > 'Z' does.  A user who misunderstands what 'Z' does could lose data due
> > to unanticipated overwrite when the archive is unpacked.  (Note that the
> > docstring for dired-do-compress says nothing about creating or unpacking
> > archive files.)
> 
> I don't think I understand.  Are you alluding to the case when the
> archive includes absolute file names, or file names that raise above
> the directory where the archive lives?  Or do you have some other case
> in mind?

The case I have in mind is where the contents of the archive are
unrelated to the name of the archive.  No absolute path or .. is
involved.  For example:

$ ls
foo.tar.gz
$ tar tfz foo.tar.gz 
a
b
c
# uncompress foo.tar.gz with 'Z'
$ ls
a  b  c  foo.tar.gz
$ 

Based on the NEWS entry, a directory "foo" should have been created and
populated with a, b, and c.  But that's not what happens, at least not
on my GNU/Linux system (Debian 9).

mike

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Eli Zaretskii]

> From: Mike Kupfer <mkupfer@alum.berkeley.edu>
> cc: 33450@debbugs.gnu.org
> Date: Wed, 21 Nov 2018 06:50:51 -0800
> 
> $ ls
> foo.tar.gz
> $ tar tfz foo.tar.gz 
> a
> b
> c
> # uncompress foo.tar.gz with 'Z'
> $ ls
> a  b  c  foo.tar.gz
> $ 
> 
> Based on the NEWS entry, a directory "foo" should have been created and
> populated with a, b, and c.  But that's not what happens, at least not
> on my GNU/Linux system (Debian 9).

Thanks, I modified the text in the Git repository to make it more
accurate; please take a look.

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Mike Kupfer]

Eli Zaretskii wrote:

> Thanks, I modified the text in the Git repository to make it more
> accurate; please take a look.

Looks good.  Thanks!

mike

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Eli Zaretskii]

> From: Mike Kupfer <mkupfer@alum.berkeley.edu>
> cc: 33450@debbugs.gnu.org
> Date: Wed, 21 Nov 2018 07:21:48 -0800
> 
> Eli Zaretskii wrote:
> 
> > Thanks, I modified the text in the Git repository to make it more
> > accurate; please take a look.
> 
> Looks good.  Thanks!

Thanks, I'm therefore closing this bug.

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Glenn Morris]

Mike Kupfer wrote:

> Also, and less important, I got the impression from the discussion on
> emacs-devel that this feature was partially introduced in Emacs 25.
> Wasn't the change in 26.1 just to make .tar.gz and .tgz behave the same?

Yes, .tar.gz is extracted in eg Emacs 25.3 but tgz isn't.

>  (Note that the docstring for dired-do-compress says nothing about
> creating or unpacking archive files.)

Indeed.

One might also ask about tar.xz, tar.bz2, cpio, rar, etc.

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Glenn Morris]

Glenn Morris wrote:

> Mike Kupfer wrote:
>
>> Also, and less important, I got the impression from the discussion on
>> emacs-devel that this feature was partially introduced in Emacs 25.
>> Wasn't the change in 26.1 just to make .tar.gz and .tgz behave the same?
>
> Yes, .tar.gz is extracted in eg Emacs 25.3 but tgz isn't.

And indeed NEWS.25 says "The command 'dired-do-compress', bound to 'Z',
now can compress directories", so NEWS.26 is duplicating that.

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Date: Wed, 21 Nov 2018 15:24:46 -0500
> Cc: 33450@debbugs.gnu.org
> 
> And indeed NEWS.25 says "The command 'dired-do-compress', bound to 'Z',
> now can compress directories", so NEWS.26 is duplicating that.

I see no harm in that, as the NEWS.26 text is more complete and
accurate (it talks about decompression as well, for starters).

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Glenn Morris]

Eli Zaretskii wrote:

>> And indeed NEWS.25 says "The command 'dired-do-compress', bound to 'Z',
>> now can compress directories", so NEWS.26 is duplicating that.
>
> I see no harm in that, as the NEWS.26 text is more complete and
> accurate (it talks about decompression as well, for starters).

I find this odd.
95% of the 'Z' NEWS.26 entry is true in Emacs 25.1 (by experiment).
The only thing that's different in 26.1 is the .tgz treatment.
This hardly seems NEWS-worthy.

If you for some reason want to keep the expanded entry in NEWS.26, it
should at least be corrected to say "This change was actually made in
Emacs 25.1, but the NEWS entry was too terse" (or however you want to
justfiy re-visiting it). It is incorrect to say "This change was
actually made in Emacs 26.1".

But I think it would be better to move your description from NEWS to the
doc string.

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Cc: mkupfer@alum.berkeley.edu,  33450@debbugs.gnu.org
> Date: Thu, 22 Nov 2018 13:18:54 -0500
> 
> Eli Zaretskii wrote:
> 
> >> And indeed NEWS.25 says "The command 'dired-do-compress', bound to 'Z',
> >> now can compress directories", so NEWS.26 is duplicating that.
> >
> > I see no harm in that, as the NEWS.26 text is more complete and
> > accurate (it talks about decompression as well, for starters).
> 
> I find this odd.
> 95% of the 'Z' NEWS.26 entry is true in Emacs 25.1 (by experiment).
> The only thing that's different in 26.1 is the .tgz treatment.
> This hardly seems NEWS-worthy.
> 
> If you for some reason want to keep the expanded entry in NEWS.26, it
> should at least be corrected to say "This change was actually made in
> Emacs 25.1, but the NEWS entry was too terse" (or however you want to
> justfiy re-visiting it). It is incorrect to say "This change was
> actually made in Emacs 26.1".
> 
> But I think it would be better to move your description from NEWS to the
> doc string.

Done.

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

I think it was a mistake to make Z operate on directories,
and a mistake to think of to creating an archive as "compression".

It would be better to use A as a command to pack and unpack
archives.

-- 
Dr Richard Stallman
President, Free Software Foundation (https://gnu.org, https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Eli Zaretskii]

> From: Richard Stallman <rms@gnu.org>
> Date: Thu, 22 Nov 2018 18:17:14 -0500
> Cc: 33450@debbugs.gnu.org, mkupfer@alum.berkeley.edu
> 
> I think it was a mistake to make Z operate on directories,
> and a mistake to think of to creating an archive as "compression".
> 
> It would be better to use A as a command to pack and unpack
> archives.

I agree, and wrote as much in the discussion.  But I'm not going to
work on that any time soon, and meanwhile we should have our
documentation describe what this command does in enough detail for
users not to be surprised.

bug#33450: 26.1.90; NEWS entry for dired 'Z' is inaccurate

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > I agree, and wrote as much in the discussion.  But I'm not going to
  > work on that any time soon, and meanwhile we should have our
  > documentation describe what this command does in enough detail for
  > users not to be surprised.

I won't dispute that.

-- 
Dr Richard Stallman
President, Free Software Foundation (https://gnu.org, https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)