Supabase first-class support

Adds zero-config Supabase project detection and a native Supabase migration
file format, so DBDiff works seamlessly inside any Supabase project without
any manual configuration.

This PR closes all remaining gaps in DBDiff's Supabase integration.

What's changed

1. Dual-write to supabase_migrations.schema_migrations

migration:up and migration:down now keep Supabase's own history table in sync. When running against a PostgreSQL target identified as a Supabase project, every applied migration is also written into supabase_migrations.schema_migrations (with ON CONFLICT DO NOTHING), and rolled-back migrations are pruned from it. This means supabase db pull and other Supabase CLI commands will see the same history as DBDiff.

2. Environment variable fallback for DSN resolution

When no explicit source/target DSN is provided, DBDiff checks SUPABASE_DB_URL → DATABASE_URL → DIRECT_URL in order. This covers CI environments (GitHub Actions, Vercel, Netlify, Railway, Fly.io) where the DSN is injected as an env var with no config change required.

3. supabase/config.toml parsing

If no DSN is found via env vars or supabase status, DBDiff parses the [db] section of supabase/config.toml to extract port (default 54322) and password (default postgres) and constructs postgresql://postgres:{password}@127.0.0.1:{port}/postgres. Supports quoted and unquoted values.

4. Drift detection in migration:status

migration:status now compares DBDiff's _dbdiff_migrations table against Supabase's supabase_migrations.schema_migrations and reports divergence:

→  20240101000001  supabase_only  — present in Supabase but not in DBDiff
←  20240201000002  dbdiff_only    — applied via DBDiff but missing from Supabase
Run migrations through DBDiff to keep both history tables in sync.

5. Supabase-aware rollback error

migration:down now gives a clear, actionable error for supabase-format migrations rather than silently failing:

Supabase-format migrations are UP-only and do not support rollback. Write a new forward migration instead, or convert to DBDiff native format (.up.sql + .down.sql).

6. Transaction lint for Supabase migrations

Before applying each supabase-format migration, DBDiff lints the SQL for BEGIN/COMMIT/ROLLBACK/START TRANSACTION/SET TRANSACTION. Supabase wraps every migration in a transaction automatically, so manual transaction statements cause errors. Warnings are surfaced in the migration result and displayed to the user, with SQL comments stripped before analysis to avoid false positives.

7. Remote DSN auto-detection from supabase link

After running supabase link, the linked project ref is recorded in .supabase/temp/project-ref. DBDiff reads this and constructs the remote DSN automatically:

• With region (pooler): postgresql://postgres.{ref}:{password}@aws-0-{region}.pooler.supabase.com:6543/postgres
• Without region (direct): postgresql://postgres:{password}@db.{ref}.supabase.co:5432/postgres

Password is resolved from the SUPABASE_DB_PASSWORD env var or falls back to a [YOUR-PASSWORD] placeholder. The full resolution chain (resolveDbUrl) is: env vars → supabase status → config.toml.

SonarQube compliance

All new code passes SonarQube analysis:

• MigrationStatusCommand::execute — cognitive complexity reduced from 22 → ~6 by extracting formatState(), buildTable(), and renderDriftWarnings() helpers
• SupabaseProjectDetector::configTomlDbUrl — complexity reduced from 17 → ~4, returns from 4 → 2, unused variable removed, credential false-positive eliminated by extracting extractTomlSection() and parseTomlDbSection() as reusable public helpers
• SupabaseProjectDetector::resolveDbUrl — returns reduced from 4 → 1 via null-coalescing chain

Files changed

Testing

OK (417 tests, 720 assertions)

All new functionality is covered by 35 new test methods. Tests run via PHP 8.3 on SQLite (unit) and are CI-compatible.

Usage examples

# Inside a Supabase project — everything is auto-detected
cd my-supabase-project

# Create a Supabase-format migration (auto-detected, or explicit)
dbdiff migration:new add_profiles
dbdiff migration:new add_profiles --format=supabase

# Status shows cross-referenced Supa? column
dbdiff migration:status --db-url "$DATABASE_URL"

# Diff auto-fills --server1-url from the local Supabase stack (supabase status),
# but --server2-url still needs to be supplied
dbdiff diff server1.mydb:server2.mydb \
  --server2-url postgres://user:pass@db.xyz.supabase.co:5432/staging