Prerequisite for `banger update`. Before swapping a staged binary
into place, the updater needs to confirm the new bangerd recognises
the running install's DB schema. Without this, an operator could end
up with a service that won't open its store after the binary swap +
restart.
* store.InspectSchemaState(path): opens the DB read-only (reusing
OpenReadOnly's mode=ro DSN), reads the schema_migrations table,
and classifies the relationship between applied and known IDs:
SchemaCompatible (lockstep), SchemaMigrationsNeeded (binary
newer, will auto-migrate on first Open), or SchemaIncompatible
(DB has applied IDs the binary doesn't know about).
Missing schema_migrations table is treated as "all migrations
pending" rather than an error — matches the fresh-install case.
* bangerd --check-migrations: opens the configured DB read-only,
prints a one-line classification, and exits 0/1/2. The exit
code is the contract:
0 — compatible
1 — migrations needed (binary newer; safe to swap)
2 — incompatible (binary older than DB; abort the swap)
Honours --system to pick between system StateDir and user mode.
* bangerdExit indirection so future tests can capture the exit
code without terminating the test process. Production points
at os.Exit.
Tests cover the four classifications: compatible (fully migrated
DB), migrations-needed (only baseline applied), incompatible
(synthetic id=99 inserted), and missing-table (fresh DB). Live
exercise on this dev host returned `migrations needed: pending [3]
(binary will apply on first Open)` and exit 1, matching the
contract.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Thales Maciel
ec6fc9d185