allow rewinding to block 0

core/genesis.go

@@ -354,7 +354,7 @@ func SetupGenesisBlockWithOverride(db ethdb.Database, triedb *triedb.Database, g
 		return newcfg, stored, errors.New("missing head header")
 	}
 	compatErr := storedcfg.CheckCompatible(newcfg, head.Number.Uint64(), head.Time)
-	if compatErr != nil && ((head.Number.Uint64() != 0 && compatErr.RewindToBlock != 0) || (head.Time != 0 && compatErr.RewindToTime != 0)) {
+	if compatErr != nil && ((head.Number.Uint64() != 0 && compatErr.RewindByBlock) || (head.Time != 0 && compatErr.RewindToTime != 0)) {
 		return newcfg, stored, compatErr
 	}
 	// Don't overwrite if the old is identical to the new

core/genesis_test.go

@@ -148,6 +148,7 @@ func testSetupGenesis(t *testing.T, scheme string) {
 				What:          "Homestead fork block",
 				StoredBlock:   big.NewInt(2),
 				NewBlock:      big.NewInt(3),
+				RewindByBlock: true,
 				RewindToBlock: 1,
 			},
 		},

params/config.go

@@ -843,6 +843,9 @@ type ConfigCompatError struct {
 	// the block number to which the local chain must be rewound to correct the error
 	RewindToBlock uint64
 
+	// the flag to tell whether it's rewinding by block or time
+	RewindByBlock bool
+
 	// the timestamp to which the local chain must be rewound to correct the error
 	RewindToTime uint64
 }
@@ -862,6 +865,7 @@ func newBlockCompatError(what string, storedblock, newblock *big.Int) *ConfigCom
 		StoredBlock:   storedblock,
 		NewBlock:      newblock,
 		RewindToBlock: 0,
+		RewindByBlock: true,
 	}
 	if rew != nil && rew.Sign() > 0 {
 		err.RewindToBlock = rew.Uint64() - 1

params/config_test.go

@@ -52,6 +52,7 @@ func TestCheckCompatible(t *testing.T) {
 				StoredBlock:   big.NewInt(0),
 				NewBlock:      nil,
 				RewindToBlock: 0,
+				RewindByBlock: true,
 			},
 		},
 		{
@@ -63,6 +64,7 @@ func TestCheckCompatible(t *testing.T) {
 				StoredBlock:   big.NewInt(0),
 				NewBlock:      big.NewInt(1),
 				RewindToBlock: 0,
+				RewindByBlock: true,
 			},
 		},
 		{
@@ -74,6 +76,7 @@ func TestCheckCompatible(t *testing.T) {
 				StoredBlock:   big.NewInt(10),
 				NewBlock:      big.NewInt(20),
 				RewindToBlock: 9,
+				RewindByBlock: true,
 			},
 		},
 		{
@@ -91,6 +94,7 @@ func TestCheckCompatible(t *testing.T) {
 				StoredBlock:   nil,
 				NewBlock:      big.NewInt(31),
 				RewindToBlock: 30,
+				RewindByBlock: true,
 			},
 		},
 		{