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Re: [tycho-dev] Reproducible version qualifier without Git-based timestamp

Hi Igor,

On 08/30/2013 07:27 PM, Igor Fedorenko wrote:
In short, comparing two bundles ignoring version qualifier is a very hard problem. You can read longer discussion that went through several alternatives, including one you suggest, in bugzilla

Thanks for this interesting link. I've gone through the discussion, and I have additional questions for which one you might already have answers. For some background, our use-case will probably not use timestamps based on last Git commit. We use Eclipse-SourceReferences to track "Where does this bundle come from" (cf Paul comment #10), and we find it comfortable to use manually managed or build-time based timestamps (and overall to reduce the criticity of choosing the right qualifier).
So given those differences between our use-case and Platform build, I still feel that the compare-ignoring-qualifier approach would fit pretty well. So here are my additional questions with my current understanding on these issues.

= What's the difficulty in comparing bundles with different qualifiers?
The MANIFEST.MF requires a "deep" comparison (we can't check only the file signature) which would read the version and compare the 3 first segments only. Also it would require to skip the comparison of the signature for MANIFEST.MF file I guess. But all other files could be compared just by their signature.
This seems possible to implement in a comparator. Am I missing another difficulty?

= What about p2 metadata?
This question is more specific to the tycho-packaging-plugin/tycho-p2-plugin. Does the replacement of just-built bundle by the baseline version also comsume p2 metadata from baseline? If yes, I guess those p2 metadata would need to be compared as well, in case the newer build has same content, but different metadata.

= About the bigger picture
Let's say I go for such an implementation, is the integration in Tycho just a matter of implementing an extension for the tycho-p2-plugin? Is it easy to plug a different comparator in Tycho?

Mickael Istria
Eclipse developer at JBoss, by Red Hat
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