Added the diff command

Signed-off-by: Lorygold <lory.goldoni@gmail.com>

Author: Lorygold

cmd/diff.go

@@ -0,0 +1,112 @@
+package cmd
+
+import (
+	"fmt"
+	"path/filepath"
+
+	"github.com/checkpoint-restore/checkpointctl/internal"
+	metadata "github.com/checkpoint-restore/checkpointctl/lib"
+	"github.com/spf13/cobra"
+)
+
+// creates the command
+func Diff() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "diff <checkpointA> <checkpointB>",
+		Short: "Compare two container checkpoints and display differences",
+		Args:  cobra.ExactArgs(2),
+		RunE:  diff,
+	}
+
+	flags := cmd.Flags()
+	flags.StringVar(
+		format,
+		"format",
+		"tree",
+		"Specify output format: tree or json",
+	)
+	flags.BoolVar(
+		psTreeCmd,
+		"ps-tree-cmd",
+		false,
+		"Include full command lines in process tree diff",
+	)
+	flags.BoolVar(
+		psTreeEnv,
+		"ps-tree-env",
+		false,
+		"Include environment variables in process tree diff",
+	)
+	flags.BoolVar(
+		files,
+		"files",
+		false,
+		"Include file descriptors in the diff",
+	)
+	flags.BoolVar(
+		sockets,
+		"sockets",
+		false,
+		"Include sockets in the diff",
+	)
+
+	return cmd
+}
+
+// diff executes the checkpoint diff logic
+func diff(cmd *cobra.Command, args []string) error {
+	checkA := args[0]
+	checkB := args[1]
+
+	requiredFiles := []string{
+		metadata.SpecDumpFile,
+		metadata.ConfigDumpFile,
+	}
+
+	if *files || *sockets || *psTreeCmd || *psTreeEnv {
+		// Include all files necessary for deep diffs
+		for _, f := range []string{"files.img", "fs-", "ids-", "fdinfo-", "pagemap-", "pages-", "mm-", "pstree.img", "core-"} {
+			requiredFiles = append(requiredFiles, filepath.Join(metadata.CheckpointDirectory, f))
+		}
+	}
+
+	// Load tasks from both checkpoints
+	tasksAVal, err := internal.CreateTasks([]string{checkA}, requiredFiles)
+	if err != nil {
+		return fmt.Errorf("failed to load checkpointA: %w", err)
+	}
+	defer internal.CleanupTasks(tasksAVal)
+
+	tasksBVal, err := internal.CreateTasks([]string{checkB}, requiredFiles)
+	if err != nil {
+		return fmt.Errorf("failed to load checkpointB: %w", err)
+	}
+	defer internal.CleanupTasks(tasksBVal)
+
+	// Convert []Task → []*Task for DiffTasks
+	tasksA := make([]*internal.Task, len(tasksAVal))
+	for i := range tasksAVal {
+		tasksA[i] = &tasksAVal[i]
+	}
+
+	tasksB := make([]*internal.Task, len(tasksBVal))
+	for i := range tasksBVal {
+		tasksB[i] = &tasksBVal[i]
+	}
+
+	// Compute diff
+	diffTasks, err := internal.DiffTasks(tasksA, tasksB, *psTreeCmd, *psTreeEnv, *files, *sockets)
+	if err != nil {
+		return fmt.Errorf("failed to compute diff: %w", err)
+	}
+
+	// Render output
+	switch *format {
+	case "tree":
+		return internal.RenderDiffTreeView(diffTasks)
+	case "json":
+		return internal.RenderDiffJSONView(diffTasks)
+	default:
+		return fmt.Errorf("invalid output format: %s", *format)
+	}
+}

internal/diff_types.go

@@ -0,0 +1,165 @@
+package internal
+
+import (
+	"encoding/json"
+	"fmt"
+	"reflect"
+)
+
+// DiffStatus describes how a task changed between two checkpoints
+type DiffStatus string
+
+const (
+	Added     DiffStatus = "added"
+	Removed   DiffStatus = "removed"
+	Modified  DiffStatus = "modified"
+	Unchanged DiffStatus = "unchanged"
+)
+
+// DiffTask represents the forensic diff of a single task/process
+type DiffTask struct {
+	// Stable identifier for matching tasks across checkpoints
+	ID string `json:"id"`
+
+	// High-level classification of the change
+	Status DiffStatus `json:"status"`
+
+	// Task state in checkpoint A (nil if Added)
+	Before *Task `json:"before,omitempty"`
+
+	// Task state in checkpoint B (nil if Removed)
+	After *Task `json:"after,omitempty"`
+
+	// Fine-grained differences detected inside the task
+	Changes []DiffChange `json:"changes,omitempty"`
+}
+
+// DiffChange represents a single detected difference.
+type DiffChange struct {
+	// Logical category of the change (pstree, files, sockets, env, cmdline, etc.)
+	Category string `json:"category"`
+
+	// Specific field or subcomponent that changed
+	Field string `json:"field"`
+
+	// Value in checkpoint A
+	Before any `json:"before,omitempty"`
+
+	// Value in checkpoint B
+	After any `json:"after,omitempty"`
+}
+
+// DiffTasks compares two sets of tasks and returns their differences.
+func DiffTasks(
+	tasksA []*Task,
+	tasksB []*Task,
+	psTreeCmd bool,
+	psTreeEnv bool,
+	files bool,
+	sockets bool,
+) ([]DiffTask, error) {
+	if tasksA == nil || tasksB == nil {
+		return nil, fmt.Errorf("nil task list provided")
+	}
+
+	// Index tasks by CheckpointFilePath for matching
+	indexA := make(map[string]*Task)
+	indexB := make(map[string]*Task)
+
+	for _, t := range tasksA {
+		indexA[t.CheckpointFilePath] = t
+	}
+	for _, t := range tasksB {
+		indexB[t.CheckpointFilePath] = t
+	}
+
+	var diffs []DiffTask
+
+	// Tasks present in A
+	for id, taskA := range indexA {
+		taskB, exists := indexB[id]
+
+		if !exists {
+			// Removed task
+			diffs = append(diffs, DiffTask{
+				ID:     id,
+				Status: Removed,
+				Before: taskA,
+			})
+			continue
+		}
+
+		// Exists in both → compare
+		if reflect.DeepEqual(taskA, taskB) {
+			diffs = append(diffs, DiffTask{
+				ID:     id,
+				Status: Unchanged,
+				Before: taskA,
+				After:  taskB,
+			})
+			continue
+		}
+
+		// Modified task
+		diffs = append(diffs, DiffTask{
+			ID:     id,
+			Status: Modified,
+			Before: taskA,
+			After:  taskB,
+			Changes: []DiffChange{
+				{
+					Category: "task",
+					Field:    "struct",
+					Before:   taskA,
+					After:    taskB,
+				},
+			},
+		})
+	}
+
+	// Tasks only in B → Added
+	for id, taskB := range indexB {
+		if _, exists := indexA[id]; exists {
+			continue
+		}
+
+		diffs = append(diffs, DiffTask{
+			ID:     id,
+			Status: Added,
+			After:  taskB,
+		})
+	}
+
+	return diffs, nil
+}
+
+// RenderDiffTreeView prints a human-readable tree of diff tasks
+func RenderDiffTreeView(diffTasks []DiffTask) error {
+	for _, dt := range diffTasks {
+		fmt.Printf("\nTask ID: %s | Status: %s\n", dt.ID, dt.Status)
+
+		if dt.Before != nil {
+			fmt.Printf("  Before checkpoint: %s\n", dt.Before.CheckpointFilePath)
+		}
+		if dt.After != nil {
+			fmt.Printf("  After checkpoint: %s\n", dt.After.CheckpointFilePath)
+		}
+
+		for _, ch := range dt.Changes {
+			fmt.Printf("  Change: [%s] %s | Before: %v | After: %v\n",
+				ch.Category, ch.Field, ch.Before, ch.After)
+		}
+	}
+	return nil
+}
+
+// RenderDiffJSONView prints diff tasks in JSON format
+func RenderDiffJSONView(diffTasks []DiffTask) error {
+	jsonData, err := json.MarshalIndent(diffTasks, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	fmt.Println(string(jsonData))
+	return nil
+}