feat: add diff-based code modifications

Overview

This PR introduces support for diff-based file modifications in CodeWhisper's AI-assisted task implementation and restructures the parsing logic for improved modularity. These enhancements allow for more efficient handling of large edits within token limits and provide a more flexible, maintainable parsing system.

Changes

Restructured parsing logic into separate modules for improved modularity and maintainability
Updated src/ai/parse-ai-codegen-response.ts to handle diff-based modifications
Modified src/git/apply-changes.ts to apply diffs when available
Updated src/types/index.ts to include diff information in AIFileInfo
Added --diff flag to the task command for opt-in diff-based updates
Added -c, --context flag to the taskcommand and task options to allow automation and improved library usage
Updated relevant test files to cover new functionality

New Features

Users can now use the --diff flag with the task command to enable diff-based updates
CodeWhisper now supports both full content replacement and diff-based modifications for changed files
New modular parsing system allows for easier maintenance and extension of parsing capabilities

Implementation Details

Created new files for parsing logic:
- src/ai/parsers/common-parser.ts: Common parsing functions used across different modes
- src/ai/parsers/full-content-parser.ts: Parser for full content mode
- src/ai/parsers/diff-parser.ts: Parser for diff-based mode
Utilized the diff library for parsing and applying patches
Enhanced error handling for cases where patches cannot be applied
Updated the dry run output to show diff previews when available

Parser Restructuring

Separated parsing logic into distinct modules to improve code organization and maintainability
Implemented a strategy pattern to switch between full content and diff-based parsing modes
Ensured backward compatibility with existing full content parsing while adding support for diff-based parsing

Testing

Added new tests to cover diff-based modification scenarios
Updated existing tests to reflect changes in file operation behavior
Created new tests for the restructured parsing modules

Documentation

Updated README.md and USAGE.md to include information about the new --diff option
Added examples demonstrating the use of diff-based updates in the documentation

Potential Impact

This change should significantly improve CodeWhisper's ability to handle larger code modifications, especially in cases where the full file content might exceed token limits. It provides users with more flexibility in how they want CodeWhisper to process and apply changes. The restructured parsing system will make it easier to maintain and extend CodeWhisper's parsing capabilities in the future.

Closes #56

gmickel / CodeWhisper