Re: Bug#504880: Disambiguate "installed" for packages

[Jonathan Nieder <jrnieder@gmail.com>]

Based on Steve’s explanation:

Russ Allbery wrote:

> 	      <p>
> 		The <tt>Depends</tt> field should also be used if the
> 		<prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
> 		require the depended-on package to be unpacked or
> 		configured in order to run, or if the dependend-on package
> 		is desirable for cleanup done by <prgn>postrm</prgn>.

Desirable is too weak.  I think this case is complicated enough to
deserve its own paragraph.

 The <tt>Depends</tt> field should also be used if the
 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
 require the depended-on package to be unpacked or
[as before ...]
 previous upgrade of the dependency failed.

 The <tt>Depends</tt> field should also be used if an
 operation that ought to be done in <prgn>postrm</prgn>
 requires the depended-on package.

> 		                    In the case of <prgn>postrm</prgn>,
> 		there are no guarantees, but the depended-on package is
> 		more likely to be available

                                    This does not
 guarantee that the depended-on package will be available
 when <prgn>postrm</prgn> is run, but it makes it more
 likely.

> 		The <prgn>postrm</prgn> script must cleanly skip actions
> 		that require a dependency if that dependency isn't
> 		available.

          The <prgn>postrm</prgn> script must gracefully
 skip actions that require a dependency if that dependency
 isn't available.  The depended-on package should ensure
 that the corresponding state is cleaned up when <em>it</em>
 is purged.

(with a pointer to the example in #mscriptsinstact)

Sensible?