feat: add automatic database migration recovery to scripts/develop (#23466)

When developers switch branches, the database may have migrations
from the other branch that don't exist in the current binary.
This causes coder server to fail at startup, leaving developers
stuck.

The develop script now detects this before starting the server:

1. Connects to postgres (starts temp embedded instance for
   built-in postgres, or uses CODER_PG_CONNECTION_URL).
2. Compares DB version against the source's latest migration.
3. If DB is ahead, searches git history for the missing down
   SQL files and applies them in a transaction.
4. If git recovery fails (ambiguous versions across branches,
   missing files), falls back to resetting the public schema.

Also adds --reset-db and --skip-db-recovery flags.

scripts/develop/main.go

@@ -119,6 +119,24 @@ func main() {
 				Description: "Starter template to create (empty to skip).",
 				Value:       serpent.StringOf(&cfg.starterTemplate),
 			},
+			{
+				Flag:        "db-rollback",
+				Env:         "CODER_DEV_DB_ROLLBACK",
+				Description: "Roll back database migrations that no longer exist on the current branch.",
+				Value:       serpent.BoolOf(&cfg.dbRollback),
+			},
+			{
+				Flag:        "db-reset",
+				Env:         "CODER_DEV_DB_RESET",
+				Description: "Destroy the development database and start fresh.",
+				Value:       serpent.BoolOf(&cfg.dbReset),
+			},
+			{
+				Flag:        "db-continue",
+				Env:         "CODER_DEV_DB_CONTINUE",
+				Description: "Accept changed migration files and update tracking. Use when you've manually fixed the DB to match the new migrations.",
+				Value:       serpent.BoolOf(&cfg.dbContinue),
+			},
 		},
 		Handler: func(inv *serpent.Invocation) error {
 			cfg.serverExtraArgs = inv.Args
@@ -152,6 +170,9 @@ type devConfig struct {
 	multiOrg        bool
 	debug           bool
 	starterTemplate string
+	dbRollback      bool
+	dbReset         bool
+	dbContinue      bool
 	projectRoot     string
 	binaryPath      string
 	configDir       string
@@ -167,6 +188,12 @@ func (c *devConfig) validate() error {
 	if c.agpl && c.multiOrg {
 		return xerrors.New("cannot use both --agpl and --multi-organization")
 	}
+	if c.dbRollback && c.dbReset {
+		return xerrors.New("cannot use both --db-rollback and --db-reset")
+	}
+	if c.dbContinue && c.dbReset {
+		return xerrors.New("cannot use both --db-continue and --db-reset")
+	}
 	for _, p := range []struct {
 		name string
 		val  int64
@@ -337,6 +364,15 @@ func develop(ctx context.Context, logger slog.Logger, cfg *devConfig) error {
 	if err := preflight(sigCtx, logger, cfg); err != nil {
 		return err
 	}
+
+	// Check the database before building. The mismatch check is
+	// a cheap file read; only starts temp postgres on actual
+	// mismatch. This avoids a wasted build cycle when the
+	// developer needs to re-run with --db-rollback or --db-reset.
+	if err := recoverDB(sigCtx, logger, cfg); err != nil {
+		return xerrors.Errorf("database recovery: %w", err)
+	}
+
 	if err := buildBinary(sigCtx, logger, cfg); err != nil {
 		return xerrors.Errorf("build: %w", err)
 	}
@@ -386,6 +422,14 @@ func develop(ctx context.Context, logger slog.Logger, cfg *devConfig) error {
 		}
 	}
 
+	// Update migration tracking after the server has applied
+	// any new migrations. This keeps the cache current so the
+	// next run detects mismatches correctly.
+	if err := updateMigrationTracking(ctx, logger, cfg); err != nil {
+		logger.Warn(ctx, "failed to update migration tracking",
+			slog.Error(err))
+	}
+
 	if cfg.useProxy {
 		if err := setupWorkspaceProxy(ctx, cfg, client, group); err != nil {
 			logger.Warn(ctx, "proxy setup failed, continuing",