Add cmd for downgrade (#173)

kubernetes/corefile-tool/README.md

@@ -12,6 +12,7 @@ Usage:
     corefile-tool default --corefile <path> [--k8sversion <k8s-ver>]
     corefile-tool deprecated --from <coredns-ver> --to <coredns-ver> --corefile <path>
     corefile-tool migrate --from <coredns-ver> --to <coredns-ver> --corefile <path> [--deprecations <true|false>]
+    corefile-tool downgrade --from <coredns-ver> --to <coredns-ver> --corefile <path>
     corefile-tool released --dockerImageId <id>
     corefile-tool unsupported --from <coredns-ver> --to <coredns-ver> --corefile <path>
     corefile-tool validversions
@@ -26,7 +27,9 @@ The following operations are supported:
 
 - `deprecated`: returns a list of plugins/options in the Corefile that have been deprecated, removed, ignored or is a new default plugin/option.
 
-- `migrate`: updates your CoreDNS corefile to be compatible with the `-to` version. Setting the `--deprecations` flag to `true` will migrate plugins/options as soon as they are announced as deprecated.  Setting the `--deprecations` flag to `false` will migrate plugins/options only once they are removed (or made a no-op).  The default is `false`. 
+- `migrate`: updates your CoreDNS corefile to be compatible with the `-to` version. Setting the `--deprecations` flag to `true` will migrate plugins/options as soon as they are announced as deprecated.  Setting the `--deprecations` flag to `false` will migrate plugins/options only once they are removed (or made a no-op).  The default is `false`.
+
+- `downgrade` : downgrades your CoreDNS corefile to be compatible with the `-to` version. It will not restore plugins/options that might have been removed or altered during an upward migration.
 
 - `released`: determines if the `--dockerImageID` was an official CoreDNS release or not.  Only official releases of CoreDNS are supported by the tool.
 
@@ -63,4 +66,8 @@ corefile-tool migrate --from 1.4.0 --to 1.5.0 --corefile /path/to/Corefile  --de
 # that are present in the current Corefile.
 corefile-tool migrate --from 1.2.2 --to 1.3.1 --corefile /path/to/Corefile  --deprecations false
 ```
+```bash
+# Downgrade CoreDNS from v1.5.0 to v1.4.0
+corefile-tool downgrade --from 1.5.0 --to 1.4.0 --corefile /path/to/Corefile
+```
 

kubernetes/corefile-tool/cmd/downgrade.go

@@ -0,0 +1,51 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/coredns/deployment/kubernetes/migration"
+
+	"github.com/spf13/cobra"
+)
+
+// NewDowngradeCmd represents the downgrade command
+func NewDowngradeCmd() *cobra.Command {
+	var migrateCmd = &cobra.Command{
+		Use:   "downgrade",
+		Short: "Downgrade your CoreDNS corefile to a previous version",
+		Example: `# Downgrade CoreDNS from v1.5.0 to v1.4.0. 
+corefile-tool downgrade --from 1.5.0 --to 1.4.0 --corefile /path/to/Corefile`,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			from, _ := cmd.Flags().GetString("from")
+			to, _ := cmd.Flags().GetString("to")
+			corefile, _ := cmd.Flags().GetString("corefile")
+
+			migrated, err := downgradeCorefileFromPath(from, to, corefile)
+			if err != nil {
+				return fmt.Errorf("error while migration: %v \n", err)
+			}
+			fmt.Println(migrated)
+			return nil
+		},
+	}
+	migrateCmd.Flags().String("from", "", "Required: The version you are migrating from. ")
+	migrateCmd.MarkFlagRequired("from")
+	migrateCmd.Flags().String("to", "", "Required: The version you are migrating to.")
+	migrateCmd.MarkFlagRequired("to")
+	migrateCmd.Flags().String("corefile", "", "Required: The path where your Corefile is located.")
+	migrateCmd.MarkFlagRequired("corefile")
+	migrateCmd.Flags().Bool("deprecations", false, "Specify whether you want to handle plugin deprecations. [True | False] ")
+
+	return migrateCmd
+}
+
+// downgradeCorefileFromPath takes the path where the Corefile is located and downgrades the Corefile to the
+// desrired version.
+func downgradeCorefileFromPath(fromCoreDNSVersion, toCoreDNSVersion, corefilePath string) (string, error) {
+	fileBytes, err := getCorefileFromPath(corefilePath)
+	if err != nil {
+		return "", err
+	}
+	corefileStr := string(fileBytes)
+	return migration.MigrateDown(fromCoreDNSVersion, toCoreDNSVersion, corefileStr)
+}

kubernetes/corefile-tool/cmd/migrate.go

@@ -43,8 +43,8 @@ corefile-tool migrate --from 1.2.2 --to 1.3.1 --corefile /path/to/Corefile  --de
 	return migrateCmd
 }
 
-// migrateCorefileFromPath takes the path where the Corefile is located and returns the deprecated plugins or directives
-// present in the Corefile.
+// migrateCorefileFromPath takes the path where the Corefile is located and migrates the Corefile to the
+// desrired version.
 func migrateCorefileFromPath(fromCoreDNSVersion, toCoreDNSVersion, corefilePath string, deprecations bool) (string, error) {
 	fileBytes, err := getCorefileFromPath(corefilePath)
 	if err != nil {

kubernetes/corefile-tool/cmd/root.go

@@ -27,6 +27,7 @@ func CorefileTool() *cobra.Command {
 		`),
 	}
 	rootCmd.AddCommand(NewMigrateCmd())
+	rootCmd.AddCommand(NewDowngradeCmd())
 	rootCmd.AddCommand(NewDefaultCmd())
 	rootCmd.AddCommand(NewDeprecatedCmd())
 	rootCmd.AddCommand(NewUnsupportedCmd())

kubernetes/corefile-tool/cmd/unsupported.go

@@ -40,7 +40,7 @@ corefile-tool unsupported --from 1.4.0 --to 1.5.0 --corefile /path/to/Corefile`,
 	return unsupportedCmd
 }
 
-// unsupportedCorefileFromPath takes the path where the Corefile is located and returns a list of  plugins
+// unsupportedCorefileFromPath takes the path where the Corefile is located and returns a list of plugins
 // that have been removed.
 func unsupportedCorefileFromPath(fromCoreDNSVersion, toCoreDNSVersion, corefilePath string) ([]migration.Notice, error) {
 	fileBytes, err := getCorefileFromPath(corefilePath)