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clarify tar format of gpgtar in documentation
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Description

The current documentation claims that the "ustar" format is used. However T5754 and other commits show that we gpgtar already creates a format that uses extensions of the ustar format like the pax headers. gpgtar can do larger files long unicode filenames and more.

So it is closer to posix in https://www.gnu.org/software/tar/manual/html_node/Formats.html#Formats

But the documentation doc/tools.texi still has

texinfo
@command{gpgtar} encrypts or signs files into an archive.  It is an
gpg-ized tar using the same format as used by PGP's PGP Zip.

@item --create
@opindex create
Put given files and directories into a vanilla ``ustar'' archive.

@item --extract
@opindex extract
Extract all files from a vanilla ``ustar'' archive. 

@item --skip-crypto
@opindex skip-crypto
Skip all crypto operations and create or extract vanilla ``ustar''
archives.

Event Timeline

bernhard set External Link to https://mstdn.social/deck/@GnuPG/113011825339406300.Aug 23 2024, 5:05 PM
werner claimed this task.
werner added projects: Documentation, gpgtar, FAQ.
werner added a subscriber: werner.

gpgtar is compatible to PGP Desktop's format which they call ZIP. This is technically ustar with the most common extensions. Don't let us go into yet another TAR format discussion.

Because a user in https://mstdn.social/deck/@GnuPG/113011825339406300 did read the documentation, I had a look in the documentation and in other public definitions (e.g. https://www.gnu.org/software/tar/manual/html_node/Formats.html#Formats) and I can understand the questions of the user.

It would be good to know from the documentation:

  • file size limitation (original ustar has 8 GiB -1)
  • file name capabilities (original ustar has 255 length)
  • can unicode be saved (yes with gpgtar)

Unless you say that https://www.gnu.org/software/tar/manual/html_node/Formats.html#Formats) is incorrect. (Then we should file a defect with them.)

What about something like `Gpgtar uses a ustar plus common extensions format", should be easy to so.