[Mageia-dev] epoch number [Was: version scheme blocks mgarepo submit]

Fri Oct 5 15:07:03 CEST 2012

'Twas brillig, and andre999 at 05/10/12 07:13 did gyre and gimble:
+> Johnny A. Solbu a écrit :
+>> On Thursday 04 October 2012 10:56, EatDirt wrote:
+>>> adding an epoch number
+>>> (that can not be removed later)
+>>
+>> I'm sure I'm not the only one confused about this epoch thing, so I'll
+>> ask.
+>> What is an epoch? (I think I know it's function, but still)
+>>
+>> And why can it not be removed once instated? No, really, why?
+>>
+> 
+> It is like a more-than-major version, which allows
+> e.g. version 3.4 with epoch 1 to be treated as more recent than
+>  version 3.5 without epoch.
+> If epoch once defined is removed in subsequent versions,
+> these subsequent versions will be treated as older than any version with
+> epoch defined, so once defined, epoch can't be removed (without changing
+> the name of the package).
+> Epoch can be increased like other version numbers, if the need arises.
+> 
+> Evidently, if a package version error is caught early enough, the use of
+> epoch can be avoided.
+
+It's also worth stating explicitly that epochs are a pain in the
+backside! They should only be added when no other solution exists. e.g.
+we would likely never use epoch to fix any issue in cauldron, only when
+we need to fix something going from mgaN to mgaN+1.
+
+The reason they are a pain is that they are, intentionally, hidden from
+view. If you have package foo-3.5 but it has an epoch of 1, then any
+package requiring foo >= 3 would have to put "Requires: foo >= 1:3" in
+the spec.
+
+Perhaps not the best example, but it's makes inter package deps a bit
+trickier.
+
+So it solves a problem, but should be used sparingly.
+
+Col
+
+
+-- 
+
+Colin Guthrie
+colin(at)mageia.org
+http://colin.guthr.ie/
+
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+