Re: [PATCH] change default --format from gnu to posix

[Mike Frysinger]

On 14 Dec 2021 11:33, Paul Eggert wrote:
> On 12/13/21 21:56, Mike Frysinger wrote:
> > for automake, the limitations in the default v7 catch people off guard (like
> > filename limits).
> 
> This is a good reason to switch formats. That being said, a downside of 
> --format=pax is that it gratuitously uses pax extensions when not needed 
> by the uses of 'tar' that we're talking about. These pax extensions can 
> cause trouble, as illustrated by Michał's analysis.
> 
> This discussion suggests the need for a new, easy-to use format option, 
> which is like '-Hpax' except that it omits atime and ctime, and omits 
> the subseconds part of mtime. Using this format would mean that pax 
> extensions won't be used unless they're needed (a file with a long name, 
> a timestamp past the year 2246, etc.) and so the tarball would be more 
> portable to platforms with older or buggy tarball extractors.
> 
> Maybe we could call this the 'art' format, for "archive reproducible 
> tarball", so that people could use 'tar -Hart' for it. Like 'ustar', 
> 'art' format would be a strict subset of 'pax' format so it would be 
> POSIX-conforming.
> 
> We could introduce the new option in the next release of GNU tar, and 
> think about changing the default format to it in a later release.
> 
> What do you think?

i like it for automake, and to help pull more of the ecosystem up to pax.
-mike

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