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Re: repotags proposal



Panu Matilainen wrote:

My 5c on the topic I've been trying to avoid because it's too flammable for my taste. I hate politics so I'm not going to get into that, I'm commenting from purely technical POV, and actually have a proposal that might make them unnecessary.

Repotags as part of release string are just plain wrong. Unlike disttag, the repotag does not have a meaningful version information in it, it's really just a fuzz-factor to somehow differentiate packages coming from different places.

The perfect repotag would actually be the package's gpg signature:
- it's not involved in version comparison
- it can't be faked by locally rebuilding a package - it's recorded in rpmdb so it's possible to see where a package came from

For depsolvers, you need some sort of priorisation mechanism anyway to make any sense out of mixed repository situation. So the repotag mostly serves as a visual clue to humans. All the major depsolvers now have some means to priorize between repositories so what the actual rpm EVR string is doesn't really matter, what's missing is the visual clue.

Now, I hereby volunteer to write a script/popt-alias/whatever that will do the necessary mapping of gpg signature into something human readable so people can diagnose their repo-mixing problems and whatnot easily. So you'd get something resembling the below:

$ repotag -q foo bar
foo-1.2-4.el5 (EPEL)
bar-2.3-1.el5 (ATrpms)

Would something like that be enough for the "repotag folks", short term?

Look like a great idea, do you plan to do at standalone tool or something based on the the Yum API, it sounds like a candidate to
yum-utils.
Long-term, more than that's needed to really solve the issues with repository mixing. One (perhaps crazy) idea is turning repotags into namespaces, and dependencies are first looked up within that namespace and only if unsolved, other namespaces are looked at in (configurable) order.

An example (please excuse the :: notation, that's not a good choice but for examples sake...): assume we have packages foo and bar which both depend on glibc, and foo additionally depends on bar. Foo and bar are available from, say, both EPEL and ATrpms:

rhel::libxml2-2.6.28-1
epel::foo-1.2-1
atrpms::foo-1.2-1
epel::bar-2.4-5
atrpms::bar-2.4-1

If you install atrpms::foo, as atrpms namespace also provides bar, that one gets selected instead of epel::bar even though it's evr is higher. The actual namespace could internally be the gpg signature, only mapped to a human readable where exposed to the user. Sound crazy enough? ;)
Yes, i sounds very crazy to me ;-) ;-) .
I dont know if this can be done without a lot of changes into RPM.
Nice to see something constructive to solve the real problems.

Tim


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