migrate: Allow migrations to request a check run

This is currently only used by upgrade_repo_v2.

internal/migrations/interface.go

@@ -6,11 +6,16 @@ import (
 	"github.com/restic/restic/internal/restic"
 )
 
+type RepositoryCheckOptions struct {
+}
+
 // Migration implements a data migration.
 type Migration interface {
 	// Check returns true if the migration can be applied to a repo.
 	Check(context.Context, restic.Repository) (bool, error)
 
+	RepoCheckOptions() *RepositoryCheckOptions
+
 	// Apply runs the migration.
 	Apply(context.Context, restic.Repository) error
 

internal/migrations/s3_layout.go

@@ -37,6 +37,10 @@ func (m *S3Layout) Check(ctx context.Context, repo restic.Repository) (bool, err
 	return true, nil
 }
 
+func (m *S3Layout) RepoCheckOptions() *RepositoryCheckOptions {
+	return nil
+}
+
 func retry(max int, fail func(err error), f func() error) error {
 	var err error
 	for i := 0; i < max; i++ {

internal/migrations/upgrade_repo_v2.go

@@ -50,6 +50,9 @@ func (*UpgradeRepoV2) Check(ctx context.Context, repo restic.Repository) (bool,
 	return isV1, nil
 }
 
+func (*UpgradeRepoV2) RepoCheckOptions() *RepositoryCheckOptions {
+	return &RepositoryCheckOptions{}
+}
 func (*UpgradeRepoV2) upgrade(ctx context.Context, repo restic.Repository) error {
 	h := restic.Handle{Type: restic.ConfigFile}