Bug#911580: [britney2] missing trigger with breaks relationship

[Niels Thykier <niels@thykier.net>]

Paul Gevers:
> Hi Gianfranco,
> 
> On Mon, 22 Oct 2018 09:45:28 +0200 Gianfranco Costamagna
> <locutusofborg@debian.org> wrote:
>> As said, britney fails to add the appropriate trigger for virtualbox
>> when a major release is out, and for this reason the ext-pack fails to
>> install reliably on ci.d.o without additional manual triggers.
>>
>> "virtualbox (>= 5.2.20-dfsg-0~) | virtualbox-5.2,  virtualbox (<< 5.2.20-dfsg-z) | virtualbox-5.2"
>>
>> should be a valid relationship.
> 
> I am staring at the britney2 code at
> https://salsa.debian.org/release-team/britney2/blob/master/britney2/installability/builder.py#L77
> and it seems there is code available to do this correctly, except it
> only does that for cases where there is no alternative (len(block) ==
> 1). I'll try to generate a test case in the test suite for this.
> 
> [...]
> 
> Paul
> 

Fair warning; I am not sure there *is* a correct solution for
"len(block) > 1" in the general case (and much less an efficient one at
that).  It is likely going to be very difficult and expensive with
almost no return for the effort.

Thanks,
~Niels