cmd/utils: require TTD and difficulty to be zero at genesis for dev mode (#29579)

cmd/utils/flags.go

@@ -1872,13 +1872,15 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 					Fatalf("Could not read genesis from database: %v", err)
 				}
 				if !genesis.Config.TerminalTotalDifficultyPassed {
-					Fatalf("Bad developer-mode genesis configuration: terminalTotalDifficultyPassed must be true in developer mode")
+					Fatalf("Bad developer-mode genesis configuration: terminalTotalDifficultyPassed must be true")
 				}
 				if genesis.Config.TerminalTotalDifficulty == nil {
-					Fatalf("Bad developer-mode genesis configuration: terminalTotalDifficulty must be specified.")
+					Fatalf("Bad developer-mode genesis configuration: terminalTotalDifficulty must be specified")
+				} else if genesis.Config.TerminalTotalDifficulty.Cmp(big.NewInt(0)) != 0 {
+					Fatalf("Bad developer-mode genesis configuration: terminalTotalDifficulty must be 0")
 				}
-				if genesis.Difficulty.Cmp(genesis.Config.TerminalTotalDifficulty) != 1 {
-					Fatalf("Bad developer-mode genesis configuration: genesis block difficulty must be > terminalTotalDifficulty")
+				if genesis.Difficulty.Cmp(big.NewInt(0)) != 0 {
+					Fatalf("Bad developer-mode genesis configuration: difficulty must be 0")
 				}
 			}
 			chaindb.Close()