Bug#623291: Clarify that dependency loops involving relations like Suggests are ok

[Jonathan Nieder <jrnieder@gmail.com>]

Package: debian-policy
Version: 3.9.2.0
Severity: minor

Hi,

>From [1]:

> Wouldn't that create a circular dependency?
> pcscd Depends: libpcsclite1
> libpcsclite1 Suggests: pcscd
>
> I fixed a similar problem in #612972 a few weeks ago.

It seems that policy uses the term dependency for all package
relationships declared in debian/control.  So unless one pays close
attention to the context, it is possible to read

	Packages should therefore avoid circular dependencies where
	possible, particularly if they have <prgn>postinst</prgn>
	scripts.

as meaning that a Depends relation in one direction with a Suggests
relation in the other direction is a circular dependency and something
to be avoided.

I do not think that is the intention.  Potential fixes:

- Use the term "relationship" instead of "dependency" throughout.  It
  is confusing to call conflicts and Breaks relations dependencies
  anyway (I guess a conflict with X is a dependency on not-X).

- Be more explicit that "circular dependencies" means chains of
  Depends relations starting and ending at the same package.  While at
  it, mention that chains of Depends and Pre-Depends relationships
  starting and ending at the same package are not allowed (in
  addition to the existing text which says "Pre-Depends does not
  permit circular dependencies to be broken").

What do you think?  If this seems like a sensible thing to do, I'd be
happy to work on a patch.

Ciao,
Jonathan

[1] http://lists.debian.org/debian-ctte/2011/04/msg00011.html