Problem

When creating pull requests using the GitHub MCP server, users frequently encounter "Unprocessable Entity" errors without clear indication of the underlying cause.

Solution

This PR improves the pull request creation process by:

1. Adding branch validation to verify both base and head branches exist
2. Checking for commit differences between branches before attempting PR creation
3. Implementing detailed error handling with full GitHub API error messages
4. Adding helpful console logging for debugging

Changes

• Added validateBranch function to verify branch existence
• Added getCommitDifference function to check for mergeable changes
• Enhanced createPullRequest with step-by-step validation
• Improved error messages with detailed GitHub API responses

Testing

The implementation has been tested with:

• Non-existent branches
• Branches without commit differences
• Valid branch combinations
• Various GitHub API error scenarios

Related Issues

Closes #259 - GitHub MCP Server Pull Request Creation Error

Notes

This change makes the PR creation process more robust and provides clearer error messages when something goes wrong.