Salvage of #35508 (@dchenk), rebased onto current main. Resolved the
tests/tools/test_stage2_hook_puid_pgid.py conflict (kept both the
envdir-creation regression test on main and the new config-migration
tests).
Docker image upgrades replace code under $INSTALL_DIR but preserve
$HERMES_HOME on the mounted volume, so the persisted config.yaml never
received the schema migrations that non-Docker `hermes update` runs
(#35406). This adds scripts/docker_config_migrate.py, invoked from
stage2-hook after first-boot seeding and before gateway services start:
it backs up config.yaml + .env, runs migrate_config(interactive=False),
and honors HERMES_SKIP_CONFIG_MIGRATION=1 for manual control.
Also fixes a latent bug in check_config_version(): it called load_config()
which deep-merges DEFAULT_CONFIG, so a legacy config with no raw
_config_version falsely reported as already-current. It now reads the raw
on-disk file so legacy configs are correctly detected for migration.
Differs from #35508 as submitted (Option B cleanup): dropped the
`_config_version` line added to cli-config.yaml.example and removed the
accompanying test_cli_config_example_declares_latest_version change-detector
test. The example is a copy-template and has no business asserting a schema
version; check_config_version() reads the user's real config.yaml, not the
example. This removes a second sync point that drifts on every version bump.
Closes#35508. Fixes#35406.
Co-authored-by: Dmitriy Cherchenko <17372886+dchenk@users.noreply.github.com>