Re: .deb format: let's use 0.939, zstd, drop bzip2

[Ansgar <ansgar@debian.org>]

On Thu, 2019-05-09 at 12:32 +0000, Jeremy Stanley wrote:
> On 2019-05-09 06:27:36 +0900 (+0900), Mike Hommey wrote:
> > On Wed, May 08, 2019 at 09:04:49PM +0000, Jeremy Stanley wrote:
> [...]
> > > Are you talking about source packages or binary packages here?
> > > The
> > > latter use ar, not tar.
> > 
> > Binary packages use both.
> > 
> > $ ar t /var/cache/apt/archives/libgcc-9-dev_9.1.0-1_amd64.deb
> > debian-binary
> > control.tar.xz
> > data.tar.xz
> 
> Ahh, yes, thanks I should have remembered that... so then my
> question becomes: is the suggestion to replace *both* ar and tar in
> the binary package format with a single flat archive, or to switch
> out the tarballs inside the ar archive but continue using ar to
> aggregate them?

`ar` needs to be replaced for the file size limitation mentioned in the
initial mail: ar represents file size as a 10 digit decimal number[1]
which limits the members (control.tar.*, data.tar.*) to ~10G.

  [1] https://en.wikipedia.org/wiki/Ar_(Unix)#File_header

Replacing `ar` is an incompatible format change.  So if we already do
an incompatible change, it is an appropriate time to bundle any other
incompatible changes (if there are any).  That is why I suggested that
it might be useful to also replace the `tar` archives with another
format.

Ansgar