Support upgrading warewulf.conf

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

internal/app/wwctl/upgrade/config/cobra.go

@@ -0,0 +1,56 @@
+package config
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+
+	"github.com/warewulf/warewulf/internal/pkg/config"
+	libupgrade "github.com/warewulf/warewulf/internal/pkg/upgrade"
+	"github.com/warewulf/warewulf/internal/pkg/util"
+)
+
+var (
+	Command = &cobra.Command{
+		DisableFlagsInUseLine: true,
+		Use:                   "config [OPTIONS]",
+		Short:                 "Upgrade an existing nodes.conf",
+		Long: `Upgrades nodes.conf from a previous version of Warewulf 4 to a format
+supported by the current version.`,
+		RunE: UpgradeNodesConf,
+	}
+
+	inputPath  string
+	outputPath string
+)
+
+func init() {
+	Command.Flags().StringVarP(&inputPath, "input-path", "i", config.ConfigFile, "Path to a legacy nodes.conf")
+	Command.Flags().StringVarP(&outputPath, "output-path", "o", config.ConfigFile, "Path to write the upgraded nodes.conf to")
+}
+
+func UpgradeNodesConf(cmd *cobra.Command, args []string) error {
+	data, err := os.ReadFile(inputPath)
+	if err != nil {
+		return err
+	}
+	legacy, err := libupgrade.ParseConfig(data)
+	if err != nil {
+		return err
+	}
+	upgraded := legacy.Upgrade()
+	if outputPath == "-" {
+		upgradedYaml, err := upgraded.Dump()
+		if err != nil {
+			return err
+		}
+		fmt.Print(string(upgradedYaml))
+		return nil
+	} else {
+		if err := util.CopyFile(outputPath, outputPath+"-old"); err != nil {
+			return err
+		}
+		return upgraded.PersistToFile(outputPath)
+	}
+}