Add ID field to Migration (parsed from INSERT INTO _migrations in Collect),
AppliedMigration type with ID+Name, and update Migrator.Applied() to return
[]AppliedMigration across all 5 backends. Matching in Up/Down/GetStatus now
checks both name and ID, so renamed migration files are still recognized as
applied if the 8-char hex ID matches.
Extract a database-agnostic migration interface (Migrator) with Collect,
Up, Down, and GetStatus orchestration. Each backend is its own Go module
to avoid dependency bloat:
- sqlmigrate: core interface, types, sentinel errors, file collection
- pgmigrate: PostgreSQL via pgx/v5
- mymigrate: MySQL/MariaDB via go-sql-driver/mysql
- litemigrate: SQLite via database/sql (caller imports driver)
- msmigrate: SQL Server via go-mssqldb
- shmigrate: shell script generation (file-path commands, not heredocs)
Integrates shmigrate into the existing cmd/sql-migrate CLI, replacing
its bespoke up/down/status logic with sqlmigrate orchestration.
