Update seed to a given height

client/commands/seeds/update.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
 
 	"github.com/tendermint/light-client/certifiers"
 
@@ -12,12 +13,13 @@ import (
 
 var updateCmd = &cobra.Command{
 	Use:          "update",
-	Short:        "Update seed to current chain state if possible",
+	Short:        "Update seed to current height if possible",
 	RunE:         commands.RequireInit(updateSeed),
 	SilenceUsage: true,
 }
 
 func init() {
+	updateCmd.Flags().Int(heightFlag, 0, "Update to this height, not latest")
 	RootCmd.AddCommand(updateCmd)
 }
 
@@ -27,14 +29,20 @@ func updateSeed(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	// get the lastest from our source
-	seed, err := certifiers.LatestSeed(cert.SeedSource)
+	h := viper.GetInt(heightFlag)
+	var seed certifiers.Seed
+	if h <= 0 {
+		// get the lastest from our source
+		seed, err = certifiers.LatestSeed(cert.SeedSource)
+	} else {
+		seed, err = cert.SeedSource.GetByHeight(h)
+	}
 	if err != nil {
 		return err
 	}
-	fmt.Printf("Trying to update to height: %d...\n", seed.Height())
 
 	// let the certifier do it's magic to update....
+	fmt.Printf("Trying to update to height: %d...\n", seed.Height())
 	err = cert.Update(seed.Checkpoint, seed.Validators)
 	if err != nil {
 		return err