Description

This PR fixes a Git reference conflict that occurs when creating temporary deployment branches. The action was failing when a branch named github-pages-deploy-action already exists in the repository.

The action creates temporary branches using the pattern:

github-pages-deploy-action/{random-string}

When a branch named github-pages-deploy-action already exists, Git cannot create the temporary branch because it interprets branch names with forward slashes as nested references. This causes the error:

fatal: cannot lock ref 'refs/heads/github-pages-deploy-action/sh2ajsxux': 'refs/heads/github-pages-deploy-action' exists; cannot create 'refs/heads/github-pages-deploy-action/sh2ajsxux'

Changed the temporary branch naming pattern from:

`github-pages-deploy-action/${randomString}`

To:

`github-pages-deploy-action-${randomString}`

This uses a hyphen separator instead of a forward slash, eliminating the Git reference conflict while maintaining a clear naming convention.

Changes Made

• src/git.ts: Modified line 111 to use hyphen instead of forward slash in temporaryDeploymentBranch
• tests/git.test.ts: Added test case to validate branch name format and prevent regression
• .github/copilot-instructions.md: Added Copilot instructions file with comprehensive repository guidelines, development practices, testing patterns, and deployment flow documentation

Testing Instructions

1. Run the test suite: yarn test - All 60 tests should pass including the new test that validates temporary branch names use hyphens
2. Build the project: yarn build - Should complete without errors
3. Run linting: yarn lint - Should pass without issues
4. Verify the new Copilot instructions file provides useful context for development

Additional Notes

This minimal change resolves the Git reference conflict without affecting any other functionality or breaking existing workflows. The addition of Copilot instructions will help improve future development and contributions to the repository.

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.