[MM-13895] Implement config migration command (#10508)

* [MM-13895] Implement config migration command

* Discarding unused error

cmd/mattermost/commands/config.go

@@ -68,8 +68,19 @@ var ConfigSetCmd = &cobra.Command{
 	RunE:    configSetCmdF,
 }
 
+var MigrateConfigCmd = &cobra.Command{
+	Use:     "migrate",
+	Short:   "Migrate existing config between backends",
+	Long:    "Migrate a file-based configuration to (or from) a database-based configuration. Point the Mattermost server at the target configuration to start using it",
+	Example: `config migrate --from=path/to/config.json --to="postgres://mmuser:mostest@dockerhost:5432/mattermost_test?sslmode=disable&connect_timeout=10"`,
+	RunE:    configMigrateCmdF,
+}
+
 func init() {
 	ConfigSubpathCmd.Flags().String("path", "", "Optional subpath; defaults to value in SiteURL")
+	MigrateConfigCmd.Flags().String("from", "", "Config from which to migrate")
+	MigrateConfigCmd.Flags().String("to", "", "Config to which to migrate")
+	MigrateConfigCmd.MarkFlagRequired("to")
 
 	ConfigCmd.AddCommand(
 		ValidateConfigCmd,
@@ -77,6 +88,7 @@ func init() {
 		ConfigGetCmd,
 		ConfigShowCmd,
 		ConfigSetCmd,
+		MigrateConfigCmd,
 	)
 	RootCmd.AddCommand(ConfigCmd)
 }
@@ -217,6 +229,40 @@ func configSetCmdF(command *cobra.Command, args []string) error {
 	return nil
 }
 
+func configMigrateCmdF(command *cobra.Command, args []string) error {
+	// Parse source config; defaults to global --config unless overwritten by --from
+	from, err := command.Flags().GetString("from")
+	if err != nil {
+		return errors.Wrap(err, "failed reading source config parameter")
+	}
+	if from == "" {
+		from = viper.GetString("config")
+	}
+
+	// Parse destination config store - MarkFlagRequired handles errors here
+	to, _ := command.Flags().GetString("to")
+
+	// Get source config store - invalid config will throw error here
+	fromConfigStore, err := config.NewStore(from, false)
+	if err != nil {
+		return errors.Wrap(err, "failed to read --from config")
+	}
+
+	// Get destination config store
+	toConfigStore, err := config.NewStore(to, false)
+	if err != nil {
+		return errors.Wrap(err, "failed to read --to config")
+	}
+
+	// Copy config from source to destination
+	_, err = toConfigStore.Set(fromConfigStore.Get())
+	if err != nil {
+		return errors.Wrap(err, "failed to migrate config")
+	}
+
+	return nil
+}
+
 func updateConfigValue(configSetting string, newVal []string, oldConfig, newConfig *model.Config) func(*model.Config) {
 	return func(update *model.Config) {
 

cmd/mattermost/commands/config_test.go

@@ -4,6 +4,8 @@
 package commands
 
 import (
+	"fmt"
+	"github.com/mattermost/mattermost-server/config"
 	"io/ioutil"
 	"os"
 	"reflect"
@@ -435,6 +437,43 @@ func TestUpdateMap(t *testing.T) {
 
 }
 
+func TestConfigMigrate(t *testing.T) {
+	th := Setup()
+	defer th.TearDown()
+
+	sqlSettings := mainHelper.GetSqlSettings()
+	sqlDSN := fmt.Sprintf("%s://%s", *sqlSettings.DriverName, *sqlSettings.DataSource)
+	fileDSN := "config.json"
+
+	ds, err := config.NewStore(sqlDSN, false)
+	require.NoError(t, err)
+	fs, err := config.NewStore(fileDSN, false)
+	require.NoError(t, err)
+
+	defer ds.Close()
+	defer fs.Close()
+
+	t.Run("Should error without --to parameter", func(t *testing.T) {
+		assert.Error(t, th.RunCommand(t, "config", "migrate", "--from", fileDSN))
+	})
+
+	t.Run("Should work passing the --to and the --from", func(t *testing.T) {
+		assert.NoError(t, th.RunCommand(t, "config", "migrate", "--from", fileDSN, "--to", sqlDSN))
+	})
+
+	t.Run("Should work passing --to and no --from (taking the default config file)", func(t *testing.T) {
+		assert.NoError(t, th.RunCommand(t, "config", "migrate", "--to", sqlDSN))
+	})
+
+	t.Run("Should fail passing an invalid --to", func(t *testing.T) {
+		assert.Error(t, th.RunCommand(t, "config", "migrate", "--from", fileDSN, "--to", "mysql://asd"))
+	})
+
+	t.Run("Should fail passing an invalid --from", func(t *testing.T) {
+		assert.Error(t, th.RunCommand(t, "config", "migrate", "--from", "invalid/path", "--to", sqlDSN))
+	})
+}
+
 func contains(configMap map[string]interface{}, v interface{}, configSettings []string) bool {
 	res := configMap[configSettings[0]]