fix: improve mergebot /update command with better fork handling and checkout

[vilsonrodrigues]

Summary

This PR fixes several critical issues with the /update command in the mergebot workflow that were causing checkout failures when trying to update PR branches.

Problems Fixed

1. Checkout was fetching from wrong repository

   • actions/checkout@v4 didn't specify the repository parameter
   • For PRs from the same repo with deleted branches, checkout would fail with "branch not found"
   • Error: A branch or tag with the name 'xxx' could not be found

2. Branch comparison used incorrect reference format

   • Used ${context.repo.owner}/${context.repo.repo}:${headBranch} format unnecessarily
   • Simpler branch reference works better for same-repo PRs

3. Fork validation happened too late

   • Fork PRs would go through validation steps before being rejected
   • Caused unnecessary operations and confusing error messages

Changes Made

1. Early Exit for Fork PRs (lines 407-430)

• Moved fork detection to "Get PR info" step
• Immediately exits with clear error message for fork PRs
• Prevents unnecessary validation and checkout attempts

2. Explicit Repository in Checkout (line 553)

uses: actions/checkout@v4
with:
  repository: ${{ steps.pr_info.outputs.head_repo }}  # ✅ Now explicit
  ref: ${{ steps.pr_info.outputs.head_branch }}

3. Simplified Branch Comparison (line 515)

// Simple reference for same-repo PRs (forks exit early)
head: headBranch

4. Optimized Validation Conditions

if: steps.check_perms.outputs.has_permission == 'true' && steps.pr_info.outputs.is_fork != 'true'

Benefits

✅ Better error handling: Fork PRs get immediate, clear feedback
✅ Fixes checkout errors: Same-repo PRs can now be updated correctly
✅ Better performance: Skips unnecessary operations for fork PRs
✅ Cleaner code: Simplified flow and reduced redundancy

Testing

To test this PR:

1. Test same-repo update: Comment /update on PR #[test-pr-number]
2. Verify fork handling: Comment /update on a fork PR to see the clear error message

Related Issues

Fixes the issue where /update command would fail with:

Error: A branch or tag with the name 'fix/logo-rendering-and-readme' could not be found

🤖 Generated with Claude Code