Move to yaml-based configuration

This commit updates the configuration to be yaml-based and updates the
configuration to read in a yaml file.

cmd/config_migrate.go

@@ -0,0 +1,64 @@
+package cmd
+
+import (
+	"bytes"
+
+	wisski_distillery "github.com/FAU-CDI/wisski-distillery"
+	"github.com/FAU-CDI/wisski-distillery/internal/cli"
+	"github.com/FAU-CDI/wisski-distillery/internal/config"
+	"github.com/FAU-CDI/wisski-distillery/internal/config/legacy"
+	"github.com/FAU-CDI/wisski-distillery/pkg/environment"
+)
+
+// ConfigMigrate is the config-migrate command
+var ConfigMigrate wisski_distillery.Command = cfgMigrate{}
+
+type cfgMigrate struct {
+	Positionals struct {
+		Input string `positional-arg-name:"input" required:"1-1" description:"old config to migrate"`
+	} `positional-args:"true"`
+}
+
+func (cfgMigrate) Description() wisski_distillery.Description {
+	return wisski_distillery.Description{
+		Requirements: cli.Requirements{
+			NeedsDistillery: false,
+		},
+		Command:     "config_migrate",
+		Description: "migrate legacy configuration",
+	}
+}
+
+func (c cfgMigrate) Run(context wisski_distillery.Context) error {
+	// migration environment is the native environment!
+	env := new(environment.Native)
+
+	// open the legacy file
+	file, err := env.Open(c.Positionals.Input)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	// migrate from a legacy configuration
+	// then marshal, and re-read
+
+	var cfg config.Config
+	{
+		var mconfig config.Config
+		var output bytes.Buffer
+
+		if err := legacy.Migrate(&mconfig, env, file); err != nil {
+			return err
+		}
+		if err := mconfig.Marshal(&output); err != nil {
+			return err
+		}
+		if err := cfg.Unmarshal(env, &output); err != nil {
+			return err
+		}
+	}
+
+	// do a final marshal
+	return cfg.Marshal(context.Stdout)
+}