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

[Mike Frysinger]

On 11 Dec 2021 18:56, Paul Eggert wrote:
> On 12/10/21 20:31, Mike Frysinger wrote:
> > i think the take away is that GNU tar moves the ecosystem.  if it changed
> > its default to pax, then projects would be more incentivized to update.
> 
> Yes, it's the classic chicken-and-egg problem.
> 
> Something along the lines of patch 1/2 looks OK, though the test for the 
> warning looks backwards: shouldn't the warning be issued when the 
> builder uses the release default instead of when the builder overrides 
> the default?

sorry, i'm not following.  the warning is issued when DEFAULT_ARCHIVE_FORMAT
has not been set by the builder, so the default value is used.  if the builder
has set a value, then no warning is shown.

$ ./configure
<warning shown>
$ ./configure DEFAULT_ARCHIVE_FORMAT=GNU
<no warning shown>

> As for patch 2/2, I expect that we'd need to give distros more warning 
> that this time we really mean it; we can't just flip a switch. That is,

i don't have a strong opinion on when the bit actually flips.  i picked "the
next release" as the easiest thing.  if you want to wait to push the change
in git until like a year after the release with the warning enabled, that's
fine.  prob want to keep the warning text "imminent" to encourage people to
not continue to ignore it.

> if we're going to do this at all (I'd certainly like Sergey's opinion here).

Sergey wrote the manual text saying the default would change :).

> Have you changed Gentoo's build procedure to configure 'tar' with 
> './configure DEFAULT_ARCHIVE_FORMAT=POSIX' when it builds 'tar'? If not, 
> I suggest doing that, and then reporting back after the revised 'tar' 
> has been used by a significant number of Gentoo users. That will help 
> build a case for making the proposed change.

i think that will trigger a bit of a flamewar.  Gentoo generally has a policy
of not deviating from upstream by default, especially when it has wide network
effects (the change doesn't affect just the user's system, but things produced
on their system and shared out with the world).  it's one reason why we tend
to be conservative when patching autotool projects that in turn show up in the
generated output.  it's one thing to make things work smoother for Gentoo, but
it's very different if those Gentoo-specific customizations escape out in the
releases made for non-Gentoo people.  i.e. i run `make dist` as an upstream
maintainer for a project, and the generated Makefile.in & ltmain.sh & such all
contain Gentoo-specific logic.

if i added an opt-in flag, i doubt enough users would flip it on such that
it'd give you the data you'd want to see.

i guess i could start putting "tar-pax" into my automake-bsaed projects.
-mike

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