feat(sync): enhance dry run content comparison with detailed debugging

- Add comprehensive logging for content comparison in batch processor
- Enhance repository file processing with size and match comparison
- Add specific VSCode settings debugging when content differs
- Update test to properly simulate existing target repo content
- Fix testifylint issue by using suite.Require().Empty instead of Len
- Improve error handling for missing existing file content

Author: mrz1836

internal/sync/batch.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync"
 	"time"
 
@@ -387,13 +388,37 @@ func (bp *BatchProcessor) processFileJobWithReporter(ctx context.Context, source
 
 	// Check if content actually changed (for existing files)
 	existingContent, err := bp.getExistingFileContent(ctx, job.DestPath)
-	if err == nil && string(existingContent) == string(transformedContent) {
-		logger.Debug("File content unchanged after transformation, skipping")
-		return fileProcessResult{
-			Change: nil,
-			Error:  internalerrors.ErrTransformNotFound,
-			Job:    job,
+	if err == nil {
+		// Enhanced logging for content comparison
+		existingStr := string(existingContent)
+		transformedStr := string(transformedContent)
+		contentMatches := existingStr == transformedStr
+
+		logger.WithFields(logrus.Fields{
+			"existing_content_size":    len(existingContent),
+			"transformed_content_size": len(transformedContent),
+			"content_matches":          contentMatches,
+		}).Debug("Comparing existing vs transformed content")
+
+		// For .vscode/settings.json specifically, add detailed content comparison when there's a mismatch
+		if strings.Contains(job.DestPath, ".vscode/settings.json") && !contentMatches {
+			logger.WithFields(logrus.Fields{
+				"existing_content":    existingStr,
+				"transformed_content": transformedStr,
+				"content_equal":       contentMatches,
+			}).Warn("VSCode settings content mismatch - displaying full content for debugging")
 		}
+
+		if contentMatches {
+			logger.Debug("File content unchanged after transformation, skipping")
+			return fileProcessResult{
+				Change: nil,
+				Error:  internalerrors.ErrTransformNotFound,
+				Job:    job,
+			}
+		}
+	} else {
+		logger.WithError(err).Debug("Could not get existing file content, treating as new file")
 	}
 
 	// Create file change

internal/sync/directory_transform_test.go

@@ -1143,8 +1143,16 @@ func (suite *DirectoryTransformTestSuite) TestVSCodeSettingsRealWorldTransformat
 
 	// Create a real engine with the actual repo transformer and a mock GitHub client
 	mockGHClient := gh.NewMockClient()
-	// Configure mock to return "file not found" for any GetFile call so all files are treated as new
-	mockGHClient.On("GetFile", mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return((*gh.FileContent)(nil), ErrFileNotFound)
+	// Configure mock to return the target content for .vscode/settings.json
+	targetSettingsContent := strings.ReplaceAll(settingsContent, "github.com/mrz1836/go-broadcast", "github.com/mrz1836/go-pre-commit")
+	mockGHClient.On("GetFile", mock.Anything, "mrz1836/go-pre-commit", ".vscode/settings.json", "").Return(&gh.FileContent{
+		Content: []byte(targetSettingsContent),
+	}, nil)
+
+	// Return "file not found" for other files so they are treated as new
+	mockGHClient.On("GetFile", mock.Anything, mock.Anything, mock.MatchedBy(func(path string) bool {
+		return path != ".vscode/settings.json"
+	}), mock.Anything).Return((*gh.FileContent)(nil), ErrFileNotFound)
 
 	realEngine := &Engine{
 		transform: &DirectoryRealTransformChain{},
@@ -1157,33 +1165,10 @@ func (suite *DirectoryTransformTestSuite) TestVSCodeSettingsRealWorldTransformat
 	)
 
 	suite.Require().NoError(err)
-	suite.Require().Len(changes, 1, "Should have exactly one file change for settings.json")
-
-	change := changes[0]
-	suite.Equal(".vscode/settings.json", change.Path)
-
-	// Verify the transformation happened correctly
-	transformedContent := string(change.Content)
-	originalContent := string(change.OriginalContent)
 
-	// Key assertion: formatting.local should be transformed
-	suite.Contains(transformedContent, `"formatting.local": "github.com/mrz1836/go-pre-commit"`,
-		"Should transform formatting.local to target repo")
-	suite.NotContains(transformedContent, `"formatting.local": "github.com/mrz1836/go-broadcast"`,
-		"Should not contain original repo in formatting.local")
+	// Since the target repo already has the correct content, the file should be skipped
+	// and no changes should be returned
+	suite.Require().Empty(changes, "Should have no file changes since content matches after transformation")
 
-	// Verify the original content contained the source repo
-	suite.Contains(originalContent, `"formatting.local": "github.com/mrz1836/go-broadcast"`,
-		"Original content should contain source repo")
-
-	// Verify no other content was changed (except the transformation)
-	suite.Contains(transformedContent, `"go.useLanguageServer": true`)
-	suite.Contains(transformedContent, `"go.lintTool": "golangci-lint"`)
-	suite.Contains(transformedContent, `"formatting.gofumpt": true`)
-
-	suite.logger.WithFields(logrus.Fields{
-		"original_length":    len(originalContent),
-		"transformed_length": len(transformedContent),
-		"file_path":          change.Path,
-	}).Info("VSCode settings transformation test completed successfully")
+	suite.logger.Info("VSCode settings transformation test completed successfully - file correctly skipped due to identical content")
 }

internal/sync/repository.go

@@ -378,9 +378,35 @@ func (rs *RepositorySync) processFile(ctx context.Context, sourcePath string, fi
 
 	// Check if content actually changed (for existing files)
 	existingContent, err := rs.getExistingFileContent(ctx, fileMapping.Dest)
-	if err == nil && string(existingContent) == string(transformedContent) {
-		rs.logger.WithField("file", fileMapping.Dest).Debug("File content unchanged, skipping")
-		return nil, internalerrors.ErrTransformNotFound
+	if err == nil {
+		// Enhanced logging for content comparison
+		existingStr := string(existingContent)
+		transformedStr := string(transformedContent)
+		contentMatches := existingStr == transformedStr
+
+		rs.logger.WithFields(logrus.Fields{
+			"file":                     fileMapping.Dest,
+			"existing_content_size":    len(existingContent),
+			"transformed_content_size": len(transformedContent),
+			"content_matches":          contentMatches,
+		}).Debug("Comparing existing vs transformed content")
+
+		// For .vscode/settings.json specifically, add detailed content comparison when there's a mismatch
+		if strings.Contains(fileMapping.Dest, ".vscode/settings.json") && !contentMatches {
+			rs.logger.WithFields(logrus.Fields{
+				"file":                fileMapping.Dest,
+				"existing_content":    existingStr,
+				"transformed_content": transformedStr,
+				"content_equal":       contentMatches,
+			}).Warn("VSCode settings content mismatch - displaying full content for debugging")
+		}
+
+		if contentMatches {
+			rs.logger.WithField("file", fileMapping.Dest).Debug("File content unchanged, skipping")
+			return nil, internalerrors.ErrTransformNotFound
+		}
+	} else {
+		rs.logger.WithError(err).WithField("file", fileMapping.Dest).Debug("Could not get existing file content, treating as new file")
 	}
 
 	return &FileChange{