repo_checker: provide indication of new dependencies for ring0 packages

[jberry-suse]

Source request: https://progress.opensuse.org/issues/15016:

Assume this scenario:

take the package util-linux: it is in ring0
a new submission comes in, that newly adds: 'BuildRequires: procps'
We add util-linux to Staging:A (as it's a ring0 package)
procps is currently in ring1
util-linux will build 'just fine' in Staging:A - as procps is there (from earlier builds)
so the staging eventually turns green
we accept util-linux into openSUSE:Factory, which in turn mean:
util-linux in Rings:0-Bootstrap can no longer build, as procps is now missing there (and we can't bootstrap the OS anymore)
there are two solutions: move procpos to ring0 (not cool: it depends on systemd-mini) or revert the change on util-linux
=> it would be good to see such breakage before we accept and have the issue effectlively in Ring0

Likely, a comment on the request and an added review for factory-maintainers or similar?

[jberry-suse]

Presumably, the new dependencies is not so much the item of interest as much as dependencies from a lower ring (ie ring-1).

[DimStar77]

I think on ring1/2 this is not so much of a problem, as those things are actually seen usually, due to the split LETTER/LETTER:DVD

The problem with ring0 packages is that they are also in LETTER (in the ring0 enabled stagings), and this simply can consume everything in ring1 - definitively not what we want.

Just had a case again today, i.e.

rpm update, new dependency on /usr/bin/python (python2-base); python2-base being a ring1 package, this would not cause any extra warning that this rpm package would completely mess up ring0 (luckily, this provoked a couple build fails, which made us catch it)

[jberry-suse]

Out of curiosity, why is the ring project separation not carried down into stagings? Would seem far more straight forward than tip-toeing around the issue.

• Staging:A:0-Bootstrap
• Staging:A:1-MinimalX
• Staging:A:2-TestDVD

That would have been seemingly the most straight forward way to setup stagings in light of rings. Presumably that would also solve the hidden dependency issue as well.

[coolo]

I don't see why we need this - wouldn't this cause the cycle to grow? @DimStar77 ?

[DimStar77]

I don't see why we need this - wouldn't this cause the cycle to grow? @DimStar77 ?

One would expect so, yes - but pretty sure the issues mentioned above were somehow not caught by it (or the cycle checker did not really work back then, also a possibility - there are still chances that OBS misses cycles - purely based on feelings)