multi: add the flag prune-revocation to perform the optional migration

config_builder.go

@@ -853,6 +853,7 @@ func (d *DefaultDatabaseBuilder) BuildDatabase(
 		channeldb.OptionDryRunMigration(cfg.DryRunMigration),
 		channeldb.OptionSetUseGraphCache(!cfg.DB.NoGraphCache),
 		channeldb.OptionKeepFailedPaymentAttempts(cfg.KeepFailedPaymentAttempts),
+		channeldb.OptionPruneRevocationLog(cfg.DB.PruneRevocation),
 	}
 
 	// We want to pre-allocate the channel graph cache according to what we

lncfg/db.go

@@ -61,6 +61,8 @@ type DB struct {
 	Postgres *postgres.Config `group:"postgres" namespace:"postgres" description:"Postgres settings."`
 
 	NoGraphCache bool `long:"no-graph-cache" description:"Don't use the in-memory graph cache for path finding. Much slower but uses less RAM. Can only be used with a bolt database backend."`
+
+	PruneRevocation bool `long:"prune-revocation" description:"Run the optional migration that prunes the revocation logs to save disk space."`
 }
 
 // DefaultDB creates and returns a new default DB config.

sample-lnd.conf

@@ -1205,6 +1205,12 @@ litecoin.node=ltcd
 ; less RAM. Can only be used with a bolt database backend.
 ; db.no-graph-cache=true
 
+; Specify whether the optional migration for pruning old revocation logs
+; should be applied. This migration will only save disk space if there are open
+; channels prior to lnd@v0.15.0.
+; db.prune-revocation=false
+
+
 [etcd]
 
 ; Etcd database host.