Add support for COPY command

commands.go

@@ -143,6 +143,7 @@ type Cmdable interface {
 	SetXX(ctx context.Context, key string, value interface{}, expiration time.Duration) *BoolCmd
 	SetRange(ctx context.Context, key string, offset int64, value string) *IntCmd
 	StrLen(ctx context.Context, key string) *IntCmd
+	Copy(ctx context.Context, sourceKey string, destKey string, db int, replace bool) *IntCmd
 
 	GetBit(ctx context.Context, key string, offset int64) *IntCmd
 	SetBit(ctx context.Context, key string, offset int64, value int) *IntCmd
@@ -1025,6 +1026,22 @@ func (c cmdable) StrLen(ctx context.Context, key string) *IntCmd {
 	return cmd
 }
 
+func (c cmdable) Copy(ctx context.Context, sourceKey, destKey string, db int, replace bool) *IntCmd {
+	var replaceArg string
+	if replace {
+		replaceArg = "REPLACE"
+	}
+	cmd := NewIntCmd(ctx,
+		"copy",
+		sourceKey,
+		destKey,
+		db,
+		replaceArg,
+	)
+	_ = c(ctx, cmd)
+	return cmd
+}
+
 //------------------------------------------------------------------------------
 
 func (c cmdable) GetBit(ctx context.Context, key string, offset int64) *IntCmd {

commands_test.go

@@ -1633,6 +1633,35 @@ var _ = Describe("Commands", func() {
 			Expect(strLen.Err()).NotTo(HaveOccurred())
 			Expect(strLen.Val()).To(Equal(int64(0)))
 		})
+
+		It("should Copy", func() {
+			set := client.Set(ctx, "key", "hello", 0)
+			Expect(set.Err()).NotTo(HaveOccurred())
+			Expect(set.Val()).To(Equal("OK"))
+
+			copy := client.Copy(ctx, "key", "newKey", 0, false)
+			Expect(copy.Err()).NotTo(HaveOccurred())
+			Expect(copy.Val()).To(Equal(int64(1)))
+
+			getOld := client.Get(ctx, "key")
+			Expect(getOld.Err()).NotTo(HaveOccurred())
+			Expect(getOld.Result()).To(Equal(redis.Nil))
+
+			getNew := client.Get(ctx, "newKey")
+			Expect(getNew.Err()).NotTo(HaveOccurred())
+			Expect(getNew.Result()).To(Equal("hello"))
+
+			// Copy over existing key should return error
+			set = client.Set(ctx, "key", "hello", 0)
+			Expect(set.Err()).NotTo(HaveOccurred())
+			Expect(set.Val()).To(Equal("OK"))
+			overwrite := client.Copy(ctx, "newKey", "key", 0, false)
+			Expect(overwrite.Err()).To(HaveOccurred())
+
+			// Overwrite is allowed when replace=rue
+			replace := client.Copy(ctx, "newKey", "key", 0, true)
+			Expect(replace.Err()).NotTo(HaveOccurred())
+		})
 	})
 
 	Describe("hashes", func() {