Move .env ownership to this repo and default CDC to pgoutput

[DmitriiAn]

Summary

~/.env is now owned by this repo instead of the provisioning templates, and every remaining hardcoded tunable moves into it. CDC defaults to the pgoutput plugin.

env-template

New file pgcopydb-helpers/env-template is the reference ~/.env. On the instance:

cp ~/env-template ~/.env
chmod 600 ~/.env

It cannot be named .env in the repo. .gitignore blocks that name to keep credentials out of git, and the templates deploy with cp -r pgcopydb-helpers/* /home/ubuntu/, where the shell glob does not match dotfiles. Naming it env-template means it deploys with the scripts and needs no template change.

Tunables moved into ~/.env

Variable	Default	Was
TABLE_JOBS	8	already moved, earlier in this PR
INDEX_JOBS	6	already moved, earlier in this PR
SPLIT_TABLES_LARGER_THAN	50GB	literal in 3 scripts
OUTPUT_PLUGIN	pgoutput	literal wal2json in 3 scripts
FILTER_FILE	~/filters.ini	literal in 5 scripts

run-migration.sh, resume-migration.sh and resume-cdc.sh now log the effective plugin, jobs, split size and filter path to migration.log.

pgoutput

planetscale/pgcopydb#58 adds the pgoutput plugin and makes it the pgcopydb default. This PR follows it. pgoutput is part of PostgreSQL core, so the source server needs no extension, and it sends about 4.5x less network volume than wal2json. Set OUTPUT_PLUGIN=wal2json to keep the previous plugin.

drop-replication-slots.sh also drops the source publication now. pgcopydb creates one named after the replication slot for pgoutput, so without this it is left behind on the source after every migration. The drop needs ownership of the publication, so the script warns and continues on failure.

Templates

The three templates no longer create ~/.env. pgcopydb-templates/README.md now gives the cp ~/env-template ~/.env steps.

Missing .env guard

No template creates ~/.env any more, so a fresh instance has none. Every script that sources it failed with a raw shell error:

/home/ubuntu/preflight-check.sh: line 21: /home/ubuntu/.env: No such file or directory

verify-migration.sh already guarded this. The same check is now in the other 13 scripts:

ERROR: ~/.env not found. Create it from the template:
  cp ~/env-template ~/.env && chmod 600 ~/.env

Docs

pgcopydb-helpers/README.md and AGENTS.md are rewritten around the env-template flow, each with a single configuration table and an output-plugin section.

Tests

No automated suite in this repo. Checked manually:

• bash -n on all helper scripts and both terraform templates: pass.
• shellcheck -S error on all helper scripts: clean, apart from the pre-existing SC2148 in filters-lib.sh.
• cfn-lint on the CloudFormation template: exit 0, no output.
• Env resolution smoke test: FILTER_FILE=~/filters.ini expands correctly through set -a; source, and defaults apply with an empty .env.
• Missing-.env guard: exits 1 with the message above.

[DmitriiAn]

@teknogeek0
I added new ~/.env variable, PUBLICATION_NAME=migration_pub, passed as --publication by run-migration.sh, resume-migration.sh and resume-cdc.sh. It has no fallback: all three exit 1 next to the existing connection-string check if it is unset, and the name must stay the same across a run and its resumes, since pgcopydb records it in the slot file but never compares it.
New section in the README - pgoutput publication (CDC only) . It has the catalog query that generates the CREATE PUBLICATION statement — matching the list pgcopydb builds itself, with a note to mirror the ~/filters.ini exclusions — and the fix for must be owner of table ....
AGENTS.md records the variable in the ~/.env example, the configuration table and the run-migration.sh defaults.