schemadiff: Clean up MySQL version from diff hints

We already now have the MySQL version in the schemadiff environment, so
we should use it from there. Having it also in the diff hints is
duplicated and confusing this way.

Signed-off-by: Dirkjan Bussink <d.bussink@gmail.com>

Author: dbussink

go/vt/schemadiff/schema.go

@@ -1003,7 +1003,7 @@ func (s *Schema) SchemaDiff(other *Schema, hints *DiffHints) (*SchemaDiff, error
 
 	// Check and assign capabilities:
 	// Reminder: schemadiff assumes a MySQL flavor, so we only check for MySQL capabilities.
-	if capableOf := capabilities.MySQLVersionCapableOf(hints.MySQLServerVersion); capableOf != nil {
+	if capableOf := capabilities.MySQLVersionCapableOf(s.env.MySQLVersion()); capableOf != nil {
 		for _, diff := range schemaDiff.UnorderedDiffs() {
 			switch diff := diff.(type) {
 			case *AlterTableEntityDiff:

go/vt/schemadiff/schema_diff_test.go

@@ -23,6 +23,9 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"vitess.io/vitess/go/mysql/collations"
+	"vitess.io/vitess/go/vt/vtenv"
 )
 
 func TestPermutations(t *testing.T) {
@@ -911,11 +914,15 @@ func TestSchemaDiff(t *testing.T) {
 	}
 	baseHints := &DiffHints{
 		RangeRotationStrategy: RangeRotationDistinctStatements,
-		MySQLServerVersion:    "8.0.32",
 	}
-	env := NewTestEnv()
 	for _, tc := range tt {
 		t.Run(tc.name, func(t *testing.T) {
+			vtenv, err := vtenv.New(vtenv.Options{
+				MySQLServerVersion: tc.mysqlServerVersion,
+			})
+			require.NoError(t, err)
+			env := NewEnv(vtenv, collations.CollationUtf8mb4ID)
+
 			if tc.fromQueries == nil {
 				tc.fromQueries = createQueries
 			}
@@ -927,11 +934,7 @@ func TestSchemaDiff(t *testing.T) {
 			require.NoError(t, err)
 			require.NotNil(t, toSchema)
 
-			hints := *baseHints
-			if tc.mysqlServerVersion != "" {
-				hints.MySQLServerVersion = tc.mysqlServerVersion
-			}
-			schemaDiff, err := fromSchema.SchemaDiff(toSchema, &hints)
+			schemaDiff, err := fromSchema.SchemaDiff(toSchema, baseHints)
 			require.NoError(t, err)
 
 			allDiffs := schemaDiff.UnorderedDiffs()

go/vt/schemadiff/types.go

@@ -137,8 +137,6 @@ type DiffHints struct {
 	TableQualifierHint          int
 	AlterTableAlgorithmStrategy int
 	EnumReorderStrategy         int
-
-	MySQLServerVersion string // Used to determine specific capabilities such as INSTANT DDL support
 }
 
 const (