Why:
The service manager could create and run postgres instances but had no
way to retarget a port explicitly, back data up, clone an instance to
another port, or move a database between instances — the user asked for
exactly these operations.
Evidence:
- "set <name> [--port N] [--host H] [--apply] [--tag T...]": explicit
registration change; running postgres requires --apply (stop → rewrite
registration → start); port availability checked against both
registrations and live listeners. Verified: 8890→8895 with data intact
and DSN updated, old port freed; refusal without --apply.
- "db backup <name> [--db X] [--out F]": pg_dump -Fc into
runtime/<name>/backups/ (0600) with pg_restore --list self-check;
"db backups" lists them.
- "db restore <name> --file F [--db X] [--force]": restores into a new db
or refuses on a non-empty target unless --force (drop with FORCE +
recreate + restore), reporting table counts afterwards. Verified all
three paths.
- "db clone <src> <dst> [--port P] [--password PW] [--tag] [--online]":
default physical clone (brief source stop, cp -a of pgdata minus
postmaster files, new registration, source restarted on its own port);
--online copies via dump/restore without stopping the source (verified
source pid unchanged). Clone lands on the requested or derived port.
- "db copy <src> <dst> [--db X] [--force]": single-database logical move
between two running instances with the same non-empty-target guard.
"db ls <name>" lists databases.
- Fixed during verification: clone/copy leaked the CLI --port into the
source restart path (source briefly came up on the clone's port); the
address overrides are now cleared inside those commands.
Impact:
All operations stay inside runtime/<name>/, append to history.jsonl, and
reuse the existing safety constraints (own-process stop, port conflicts
reported not seized, secrets in 0600 files). Overwriting a non-empty
database requires an explicit --force everywhere. Makefile help line
mentions the new db subcommands.
Refs: .task/feature-svc-db-ops.md（任务卡=PR 描述）
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