Faster config, migrations and functions on branches

Supabase explains how its branching system provisions a new preview branch with configuration, database schema, and Edge Functions, mostly in parallel, within about 20 seconds median.

• A branch gets its inputs either from a connected GitHub repository or from the main project, depending on whether it is git-linked.
• The configuration step copies Postgres, Auth, Data API, Realtime, and Storage settings from the main project, then applies repo-specific overrides if a config.toml exists.
• Migrations are pulled from the repo or from the main project's migration history, then run as individual transactions against the branch database.