Implement merge validation logic (bd-192)

- Add merge command with --into and --dry-run flags
- Validate target and source issues exist
- Validate no self-merge attempts
- Add comprehensive test coverage
- Capture --id flag feature request as bd-9369

Amp-Thread-ID: https://ampcode.com/threads/T-22945597-9f4f-413b-afde-dcf3099eb2f0
Co-authored-by: Amp <amp@ampcode.com>

.beads/issues.jsonl

@@ -1018,7 +1018,7 @@
 {"id":"bd-1917","title":"Agent 5 Issue 74","description":"","status":"open","priority":2,"issue_type":"task","created_at":"2025-10-21T16:55:03.368848-07:00","updated_at":"2025-10-21T16:55:03.368848-07:00"}
 {"id":"bd-1918","title":"Agent 5 Issue 75","description":"","status":"open","priority":2,"issue_type":"task","created_at":"2025-10-21T16:55:03.370049-07:00","updated_at":"2025-10-21T16:55:03.370049-07:00"}
 {"id":"bd-1919","title":"Agent 5 Issue 76","description":"","status":"open","priority":2,"issue_type":"task","created_at":"2025-10-21T16:55:03.371221-07:00","updated_at":"2025-10-21T16:55:03.371221-07:00"}
-{"id":"bd-192","title":"Implement merge validation logic","description":"Validate merge operations: check for circular merges, self-merge, non-existent issues, and other edge cases","notes":"Simplified: no schema field needed. Just validate issues exist and no self-merge. Close reason pattern: 'Merged into bd-X'","status":"open","priority":1,"issue_type":"task","created_at":"2025-10-21T16:26:07.513032-07:00","updated_at":"2025-10-21T17:46:47.498332-07:00"}
+{"id":"bd-192","title":"Implement merge validation logic","description":"Validate merge operations: check for circular merges, self-merge, non-existent issues, and other edge cases","notes":"Simplified: no schema field needed. Just validate issues exist and no self-merge. Close reason pattern: 'Merged into bd-X'","status":"closed","priority":1,"issue_type":"task","created_at":"2025-10-21T16:26:07.513032-07:00","updated_at":"2025-10-21T17:51:24.046249-07:00","closed_at":"2025-10-21T17:51:24.046249-07:00"}
 {"id":"bd-1920","title":"Agent 5 Issue 77","description":"","status":"open","priority":2,"issue_type":"task","created_at":"2025-10-21T16:55:03.372421-07:00","updated_at":"2025-10-21T16:55:03.372421-07:00"}
 {"id":"bd-1921","title":"Agent 5 Issue 78","description":"","status":"open","priority":2,"issue_type":"task","created_at":"2025-10-21T16:55:03.373638-07:00","updated_at":"2025-10-21T16:55:03.373638-07:00"}
 {"id":"bd-1922","title":"Agent 5 Issue 79","description":"","status":"open","priority":2,"issue_type":"task","created_at":"2025-10-21T16:55:03.374841-07:00","updated_at":"2025-10-21T16:55:03.374841-07:00"}

cmd/bd/merge.go

@@ -0,0 +1,126 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/fatih/color"
+	"github.com/spf13/cobra"
+)
+
+var mergeCmd = &cobra.Command{
+	Use:   "merge [source-id...] --into [target-id]",
+	Short: "Merge duplicate issues into a single issue",
+	Long: `Merge one or more source issues into a target issue.
+
+This command:
+1. Validates all issues exist and no self-merge
+2. Closes source issues with reason 'Merged into bd-X'
+3. Migrates all dependencies from sources to target
+4. Updates text references in all issue descriptions/notes
+
+Example:
+  bd merge bd-42 bd-43 --into bd-42
+  bd merge bd-10 bd-11 bd-12 --into bd-10 --dry-run`,
+	Args: cobra.MinimumNArgs(1),
+	Run: func(cmd *cobra.Command, args []string) {
+		targetID, _ := cmd.Flags().GetString("into")
+		if targetID == "" {
+			fmt.Fprintf(os.Stderr, "Error: --into flag is required\n")
+			os.Exit(1)
+		}
+
+		sourceIDs := args
+		dryRun, _ := cmd.Flags().GetBool("dry-run")
+
+		// Validate merge operation
+		if err := validateMerge(targetID, sourceIDs); err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			os.Exit(1)
+		}
+
+		// TODO: Add RPC support when daemon implements MergeIssues
+		if daemonClient != nil {
+			fmt.Fprintf(os.Stderr, "Error: merge command not yet supported in daemon mode (see bd-190)\n")
+			os.Exit(1)
+		}
+
+		// Direct mode
+		ctx := context.Background()
+
+		if dryRun {
+			if !jsonOutput {
+				fmt.Println("Dry run - validation passed, no changes made")
+				fmt.Printf("Would merge: %s into %s\n", strings.Join(sourceIDs, ", "), targetID)
+			}
+			return
+		}
+
+		// Perform merge
+		if err := performMerge(ctx, targetID, sourceIDs); err != nil {
+			fmt.Fprintf(os.Stderr, "Error performing merge: %v\n", err)
+			os.Exit(1)
+		}
+
+		// Schedule auto-flush
+		markDirtyAndScheduleFlush()
+
+		if jsonOutput {
+			result := map[string]interface{}{
+				"target_id":  targetID,
+				"source_ids": sourceIDs,
+				"merged":     len(sourceIDs),
+			}
+			outputJSON(result)
+		} else {
+			green := color.New(color.FgGreen).SprintFunc()
+			fmt.Printf("%s Merged %d issue(s) into %s\n", green("✓"), len(sourceIDs), targetID)
+		}
+	},
+}
+
+func init() {
+	mergeCmd.Flags().String("into", "", "Target issue ID to merge into (required)")
+	mergeCmd.Flags().Bool("dry-run", false, "Validate without making changes")
+	rootCmd.AddCommand(mergeCmd)
+}
+
+// validateMerge checks that merge operation is valid
+func validateMerge(targetID string, sourceIDs []string) error {
+	ctx := context.Background()
+
+	// Check target exists
+	target, err := store.GetIssue(ctx, targetID)
+	if err != nil {
+		return fmt.Errorf("target issue not found: %s", targetID)
+	}
+	if target == nil {
+		return fmt.Errorf("target issue not found: %s", targetID)
+	}
+
+	// Check all sources exist and validate no self-merge
+	for _, sourceID := range sourceIDs {
+		if sourceID == targetID {
+			return fmt.Errorf("cannot merge issue into itself: %s", sourceID)
+		}
+
+		source, err := store.GetIssue(ctx, sourceID)
+		if err != nil {
+			return fmt.Errorf("source issue not found: %s", sourceID)
+		}
+		if source == nil {
+			return fmt.Errorf("source issue not found: %s", sourceID)
+		}
+	}
+
+	return nil
+}
+
+// performMerge executes the merge operation
+func performMerge(ctx context.Context, targetID string, sourceIDs []string) error {
+	// TODO: Implement actual merge logic in bd-190
+	// This is a placeholder for validation purposes
+	return fmt.Errorf("merge operation not yet implemented (see bd-190)")
+}

cmd/bd/merge_test.go

@@ -0,0 +1,182 @@
+package main
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/steveyegge/beads/internal/storage/sqlite"
+	"github.com/steveyegge/beads/internal/types"
+)
+
+func TestValidateMerge(t *testing.T) {
+	tmpDir := t.TempDir()
+	dbFile := filepath.Join(tmpDir, ".beads", "issues.db")
+	if err := os.MkdirAll(filepath.Dir(dbFile), 0755); err != nil {
+		t.Fatalf("Failed to create test directory: %v", err)
+	}
+
+	testStore, err := sqlite.New(dbFile)
+	if err != nil {
+		t.Fatalf("Failed to create test storage: %v", err)
+	}
+	defer testStore.Close()
+
+	store = testStore
+	ctx := context.Background()
+
+	// Create test issues
+	issue1 := &types.Issue{
+		ID:          "bd-1",
+		Title:       "Test issue 1",
+		Description: "Test",
+		Priority:    1,
+		IssueType:   types.TypeTask,
+		Status:      types.StatusOpen,
+	}
+	issue2 := &types.Issue{
+		ID:          "bd-2",
+		Title:       "Test issue 2",
+		Description: "Test",
+		Priority:    1,
+		IssueType:   types.TypeTask,
+		Status:      types.StatusOpen,
+	}
+	issue3 := &types.Issue{
+		ID:          "bd-3",
+		Title:       "Test issue 3",
+		Description: "Test",
+		Priority:    1,
+		IssueType:   types.TypeTask,
+		Status:      types.StatusOpen,
+	}
+
+	if err := testStore.CreateIssue(ctx, issue1, "test"); err != nil {
+		t.Fatalf("Failed to create issue1: %v", err)
+	}
+	if err := testStore.CreateIssue(ctx, issue2, "test"); err != nil {
+		t.Fatalf("Failed to create issue2: %v", err)
+	}
+	if err := testStore.CreateIssue(ctx, issue3, "test"); err != nil {
+		t.Fatalf("Failed to create issue3: %v", err)
+	}
+
+	tests := []struct {
+		name      string
+		targetID  string
+		sourceIDs []string
+		wantErr   bool
+		errMsg    string
+	}{
+		{
+			name:      "valid merge",
+			targetID:  "bd-1",
+			sourceIDs: []string{"bd-2", "bd-3"},
+			wantErr:   false,
+		},
+		{
+			name:      "self-merge error",
+			targetID:  "bd-1",
+			sourceIDs: []string{"bd-1"},
+			wantErr:   true,
+			errMsg:    "cannot merge issue into itself",
+		},
+		{
+			name:      "self-merge in list",
+			targetID:  "bd-1",
+			sourceIDs: []string{"bd-2", "bd-1"},
+			wantErr:   true,
+			errMsg:    "cannot merge issue into itself",
+		},
+		{
+			name:      "nonexistent target",
+			targetID:  "bd-999",
+			sourceIDs: []string{"bd-1"},
+			wantErr:   true,
+			errMsg:    "target issue not found",
+		},
+		{
+			name:      "nonexistent source",
+			targetID:  "bd-1",
+			sourceIDs: []string{"bd-999"},
+			wantErr:   true,
+			errMsg:    "source issue not found",
+		},
+		{
+			name:      "multiple sources valid",
+			targetID:  "bd-1",
+			sourceIDs: []string{"bd-2"},
+			wantErr:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := validateMerge(tt.targetID, tt.sourceIDs)
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("validateMerge() expected error, got nil")
+				} else if tt.errMsg != "" && !contains(err.Error(), tt.errMsg) {
+					t.Errorf("validateMerge() error = %v, want error containing %v", err, tt.errMsg)
+				}
+			} else {
+				if err != nil {
+					t.Errorf("validateMerge() unexpected error: %v", err)
+				}
+			}
+		})
+	}
+}
+
+func TestValidateMergeMultipleSelfReferences(t *testing.T) {
+	tmpDir := t.TempDir()
+	dbFile := filepath.Join(tmpDir, ".beads", "issues.db")
+	if err := os.MkdirAll(filepath.Dir(dbFile), 0755); err != nil {
+		t.Fatalf("Failed to create test directory: %v", err)
+	}
+
+	testStore, err := sqlite.New(dbFile)
+	if err != nil {
+		t.Fatalf("Failed to create test storage: %v", err)
+	}
+	defer testStore.Close()
+
+	store = testStore
+	ctx := context.Background()
+
+	issue1 := &types.Issue{
+		ID:          "bd-10",
+		Title:       "Test issue 10",
+		Description: "Test",
+		Priority:    1,
+		IssueType:   types.TypeTask,
+		Status:      types.StatusOpen,
+	}
+
+	if err := testStore.CreateIssue(ctx, issue1, "test"); err != nil {
+		t.Fatalf("Failed to create issue: %v", err)
+	}
+
+	// Test merging multiple instances of same ID (should catch first one)
+	err = validateMerge("bd-10", []string{"bd-10", "bd-10"})
+	if err == nil {
+		t.Error("validateMerge() expected error for duplicate self-merge, got nil")
+	}
+	if !contains(err.Error(), "cannot merge issue into itself") {
+		t.Errorf("validateMerge() error = %v, want error containing 'cannot merge issue into itself'", err)
+	}
+}
+
+func contains(s, substr string) bool {
+	return len(s) >= len(substr) && (s == substr || len(s) > len(substr) && containsSubstring(s, substr))
+}
+
+func containsSubstring(s, substr string) bool {
+	for i := 0; i <= len(s)-len(substr); i++ {
+		if s[i:i+len(substr)] == substr {
+			return true
+		}
+	}
+	return false
+}