Fix the test suite by adding new "m" flags to debug output
In "Restore ?garbage by calling MarkAndSweep before parsing" I
made install code run MarkAndSweep before parsing arguments such
that the "?garbage" pattern works correctly.
This caused test suite breakage because packages now ended up
with marked flags in the debug output. Hence add "m" to the output
we assert where necessary.
In a nicer world we might want to just do MarkAndSweep if we actually
have a ?garbage pattern to evaluate but that is a bit unpredictable
in terms of performance expectations and because a "read-only" construct
modifies the depcache, so let's go with the more expected option for now
Compare SHA256 to check if versions are really the same
If we know both SHA256, and they're different, the packages are. This
approach stores the SHA256 only at runtime, avoiding the overhead of
storing it on-disk, because when we update repositories we update all
of them anyhow.
Note that pkgCacheGenerator is hidden, so we can just modify its
ABI, hooray.
