openStore runs MigrateUp on every start and logged nothing, so a schema
change was invisible. When gitbay.org turned out to be at user_version 27
before 0027 had merged, nothing in the journal connected that to the deploy
that did it — pinning it down took strings /usr/local/bin/gitbayd.
Now it reads the version either side of MigrateUp and logs schema migrated from=N to=M when they differ. An already-current database stays silent, so a
routine restart does not claim a migration that did not happen. The migrate
subcommand is unaffected: it already prints its result.
Test covers both directions, and was checked against the unpatched function to confirm it fails without the log line.
Ref #28.