Re: Zero epoch vs no epoch (patch)

On Sat, 29 Apr 2006, Christoph Thiel wrote:

> On Sat, 29 Apr 2006, Panu Matilainen wrote:
>
>>>>  - Even if no epoch is specified, the metadata still specifies this
>>>>    as "0".  For most code paths this is no problem as for all
>>>>    comparisons of version data, a missing epoch is the same as a "0"
>>>>    epoch. This should not be a huge problem and would be only a
>>>>    cleanup item for the repodata.
>>>
>>> what does removing 0-epoch items buy us?
>>
>> What it buys is support for ancient rpm versions. Remember those
>> monstrosities where non-existing epoch is not equal to zero epoch, epoch
>> promotion and all that fun? I couldn't personally care less about the
>> old rpm versions but there are people who do care, for example Dag and
>> Matthias:
>> http://lists.freshrpms.net/pipermail/freshrpms-list/2006-April/014022.html
>>
>> Removing those zero epochs from repodata makes yum rather unhappy, dunno
>> about smart, so changing the default is not really a possibility. But
>> then neither supports the prehistoric versions that are of concern here.
>> Attached quick hack of a patch adds a switch to turn off adding those
>> artificial zero epochs, using this as necessary this should be enough to
>> allow using repodata with full rpm 3.0.x - 4.4.x range.
>
> When we were implementing rpm-md support for our online update channels,
> we stumbled over the epoch thingy as well, but had to add the epoch="0",
> to keep yum & smart intact. The funny thing we found was the fact that rpm
> itself doesn't handel an empty epoch consistently -- if there is any
> interest, I'll dig into the rpm code again to give you the details...

IIRC rpm 4.2.1 was the first version of rpm to handle zero vs no epoch 
equally and sanely, except for a bug in "freshen" case where it did matter 
for rpm itself until recently (fixed last year or so). Other than the 
freshen issue (which didn't affect depsolvers) I'm not aware of any 
*recent* issues wrt epochs. Before rpm 4.2.1 there was the promote-epoch 
behavior on by default and whatnot.. a horrid mess especially thinking 
about it afterwards :)

 	- Panu -