Added image comparison functionality (#361)

* Added image comparison functionality

* enhanced partition sorting in image comparison

* Removed dead code

* fixing lint issues

* addressing failed UT and lint issues

* Added additional go-tests

* Added GPT disk/partition GUIDs to image comparison output

---------

Co-authored-by: yockgen <yock.gen.mah@intel.com>

Author: magerstam

cmd/os-image-composer/compare_cmd.go

@@ -0,0 +1,129 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	"github.com/open-edge-platform/os-image-composer/internal/image/imageinspect"
+	"github.com/open-edge-platform/os-image-composer/internal/utils/logger"
+	"github.com/spf13/cobra"
+)
+
+// Output format command flags
+var (
+	prettyDiffJSON bool   = true // Pretty-print JSON output
+	outFormat      string        // "text" | "json"
+	outMode        string = ""   // "full" | "diff" | "summary"
+)
+
+// createCompareCommand creates the compare subcommand
+func createCompareCommand() *cobra.Command {
+	compareCmd := &cobra.Command{
+		Use:   "compare [flags] IMAGE_FILE1 IMAGE_FILE2",
+		Short: "compares two RAW image files",
+		Long: `Compare performs a deep comparison of two generated
+		RAW images and provides useful details of the differences such as
+		partition table layout, filesystem type, bootloader type and 
+		configuration and overall SBOM details if available.`,
+		Args: cobra.ExactArgs(2),
+
+		RunE:              executeCompare,
+		ValidArgsFunction: templateFileCompletion,
+	}
+
+	// Add flags
+	compareCmd.Flags().BoolVar(&prettyDiffJSON, "pretty", true,
+		"Pretty-print JSON output (only for --format json)")
+	compareCmd.Flags().StringVar(&outFormat, "format", "text",
+		"Output format: text or json")
+	compareCmd.Flags().StringVar(&outMode, "mode", "",
+		"Output mode: full, diff, or summary (default: diff for text, full for json)")
+	return compareCmd
+}
+
+func resolveDefaults(format, mode string) (string, string) {
+	format = strings.ToLower(format)
+	mode = strings.ToLower(mode)
+
+	// Set default mode if not specified
+	if mode == "" {
+		if format == "json" {
+			mode = "full"
+		} else {
+			mode = "diff"
+		}
+	}
+	return format, mode
+}
+
+// executeCompare handles the compare command execution logic
+func executeCompare(cmd *cobra.Command, args []string) error {
+	log := logger.Logger()
+	imageFile1 := args[0]
+	imageFile2 := args[1]
+	log.Infof("Comparing image files: %s and %s", imageFile1, imageFile2)
+
+	inspector := newInspector()
+
+	image1, err1 := inspector.Inspect(imageFile1)
+	if err1 != nil {
+		return fmt.Errorf("image inspection failed: %v", err1)
+	}
+	image2, err2 := inspector.Inspect(imageFile2)
+	if err2 != nil {
+		return fmt.Errorf("image inspection failed: %v", err2)
+	}
+
+	compareResult := imageinspect.CompareImages(image1, image2)
+
+	format, mode := resolveDefaults(outFormat, outMode)
+
+	switch format {
+	case "json":
+		var payload any
+		switch mode {
+		case "full":
+			payload = &compareResult
+		case "diff":
+			payload = struct {
+				Equal bool                   `json:"equal"`
+				Diff  imageinspect.ImageDiff `json:"diff"`
+			}{Equal: compareResult.Equal, Diff: compareResult.Diff}
+		case "summary":
+			payload = struct {
+				Equal   bool                        `json:"equal"`
+				Summary imageinspect.CompareSummary `json:"summary"`
+			}{Equal: compareResult.Equal, Summary: compareResult.Summary}
+		default:
+			return fmt.Errorf("invalid --mode %q (expected diff|summary|full)", mode)
+		}
+		return writeCompareResult(cmd, payload, prettyDiffJSON)
+
+	case "text":
+		return imageinspect.RenderCompareText(cmd.OutOrStdout(), &compareResult,
+			imageinspect.CompareTextOptions{Mode: mode})
+
+	default:
+		return fmt.Errorf("invalid --mode %q (expected text|json)", outMode)
+	}
+}
+
+func writeCompareResult(cmd *cobra.Command, v any, pretty bool) error {
+	out := cmd.OutOrStdout()
+
+	var (
+		b   []byte
+		err error
+	)
+	if pretty {
+		b, err = json.MarshalIndent(v, "", "  ")
+	} else {
+		b, err = json.Marshal(v)
+	}
+	if err != nil {
+		return fmt.Errorf("marshal json: %w", err)
+	}
+	_, _ = fmt.Fprintln(out, string(b))
+	return nil
+}