Re: Bug#758234: debian-policy: allow packages to depend on packages of lower priority

[Charles Plessy <plessy@debian.org>]

Le Sun, Jul 02, 2017 at 01:39:13PM -0700, Russ Allbery a écrit :
> Control: tags -1 = pending
> Control: tags 759260 = pending
> Control: tags 660249 = pending
 
> The upgrading-checklist entry for this change:
> 
>           <para>
>             Priorities are now used only for controlling which packages
>             are part of a minimal or standard Debian installation and
>             should be selected based on functionality provided directly to
>             users (so nearly all shared libraries should have a priority
>             of <literal>optional</literal>).  Packages may now depend on
>             packages with a lower priority.
>           </para>
>           <para>
>             The <literal>extra</literal> priority has been deprecated and
>             should be treated as equivalent to
>             <literal>optional</literal>.  All <literal>extra</literal>
>             priorities should be changed to <literal>optional</literal>.
>             Packages with a priority of <literal>optional</literal> may
>             conflict with each other (but packages that both have a
>             priority of <literal>standard</literal> or higher still may
>             not conflict).
>           </para>

Thanks Russ and everybody who made it happen.

I am a bit late, but I would like to make two comments.

First, minor point, but I think that  #196367 (Clarify Policy on priority
inversion in dependencies) can also be closed by the changes.

Second, I would like to propose one more clarification to the description
of the "Important" priority.  At the moment, it contains the following:

    "If the expectation is that an experienced Unix person who found it missing
    would say "What on earth is going on, where is foo?", it must be an important
    package. [Footnote: This is an important criterion because we are trying to
    produce, amongst other things, a free Unix.]"

This has been written roughly 20 years ago and I think that as of today,
the diversity of experiences and evolutions of "Unix" make this definition
very hard to follow.  Also, it makes the difference between "important" and
"standard" quite blurry and matter of taste and opinions.

In contrast, the definition of "required" is very straigthforward: the bare
minimum needed to run dpkg.  Interstingly, after a quick look at the list of
"important" packages, I have the impression that they are close to the minimum
needed to run apt over the network.  If you agree with my analysis, I think
that the Policy would be clearer with this alternative definition for
"important":

    Packages which are necessary to run `apt` and use it to download other
    packages from the network, plus the bare minimum of commonly-expected and
    necessary tools to administrate the system.  This does not include
    space-consuming features such as documentationa and multilingual support.

(The last sentence above is there because man-db, debian-faq and locales are
all priority:standard).

Have a nice day,

-- 
Charles Plessy
Tsurumi, Kanagawa, Japan