Merge Resolver

Merge Resolver

Resolve merge conflicts by analyzing git history and commit intent.

Triggers

Use this skill when you encounter:

• resolve merge conflicts for PR #123
• PR has conflicts with main
• can't merge - conflicts detected
• fix the merge conflicts in this branch
• help me resolve conflicts for this pull request

Process

Phase 1: Context Gathering

Phase 2: Analysis and Resolution

Phase 3: Validation (BLOCKING)

Workflow (Quick Reference)

1. Fetch PR context - Get title, description, commits
2. Identify conflicts - Find conflicted files in working directory
3. Analyze each conflict - Use git blame and commit messages
4. Determine intent - Classify changes by type
5. Apply resolution - Keep, merge, or discard based on analysis
6. Stage resolved files - Prepare for commit
7. Validate session protocol - BLOCKING: Run validation before push

Step 1: Fetch PR Context

# Get PR metadata
gh pr view <number> --json title,body,commits,headRefName,baseRefName

# Checkout the PR branch
gh pr checkout <number>

# Attempt merge with base (creates conflict markers)
git merge origin/<base-branch> --no-commit

Step 2: Identify Conflicts

# List conflicted files
git diff --name-only --diff-filter=U

# Show conflict details
git status --porcelain | grep "^UU"

Step 3: Analyze Each Conflict

For each conflicted file:

# View the conflict
git diff --check

# Get blame for conflicting lines (base version)
git blame <base-branch> -- <file> | grep -n "<line-content>"

# Get blame for conflicting lines (head version)
git blame HEAD -- <file> | grep -n "<line-content>"

# Show commits touching this file on each branch
git log --oneline <base-branch>..<head-branch> -- <file>
git log --oneline <head-branch>..<base-branch> -- <file>

# View specific commit details
git show --stat <commit-sha>

Step 4: Determine Intent

Classify each side's changes:

Step 5: Apply Resolution

Decision Framework:

1. Same intent, compatible changes - Merge both
2. Bugfix vs feature - Bugfix wins, integrate feature around it
3. Conflicting logic - Prefer the more recent or more tested change
4. Style conflicts - Accept either, prefer consistency with surrounding code
5. Deletions vs modifications - Investigate why; deletion usually intentional

Resolution Commands:

# Accept theirs (base branch)
git checkout --theirs <file>

# Accept ours (PR branch)
git checkout --ours <file>

# Manual edit then mark resolved
git add <file>

For manual resolution:

1. Open file in editor
2. Remove conflict markers (<<<<<<<, =======, >>>>>>>)
3. Combine changes logically based on intent analysis
4. Verify syntax and logic
5. Stage the file

Step 6: Stage and Verify

# Stage all resolved files
git add <resolved-files>

# Verify no remaining conflicts
git diff --check

# Show staged changes
git diff --cached --stat

Step 7: Validate Session Protocol (BLOCKING)

MUST complete before pushing. This step prevents CI failures from incomplete session logs.

Why This Matters

Session protocol validation is a CI blocking gate. Pushing without completing session requirements causes:

• CI failures with "MUST requirement(s) not met" errors
• Wasted review cycles
• Confusion about root cause (often misidentified as template sync issues)

Validation Steps

# 1. Ensure session log exists
SESSION_LOG=$(ls -t .agents/sessions/*.md 2>/dev/null | head -1)
if [ -z "$SESSION_LOG" ]; then
    echo "ERROR: No session log found. Create one before pushing."
    exit 1
fi

# 2. Run session protocol validator
pwsh scripts/Validate-SessionJson.ps1 -SessionLogPath "$SESSION_LOG"

# 3. If validation fails, fix issues before proceeding
if [ $? -ne 0 ]; then
    echo "ERROR: Session protocol validation failed."
    echo "Complete all MUST requirements in your session log before pushing."
    exit 1
fi

Session End Checklist (REQUIRED)

Before pushing, verify your session log contains:

Common Failures

Resolution Strategies

See references/strategies.md for detailed patterns:

Code Conflicts:

• Combining additive changes
• Handling moved code
• Resolving import conflicts
• Dealing with deleted code
• Conflicting logic resolution

Infrastructure Conflicts:

• Package lock files (regenerate, don't merge)
• Configuration files (JSON/YAML semantic merge)
• Database migrations (renumber, preserve order)

Documentation Conflicts:

• Numbered documentation (ADR, RFC) - renumber incoming to next available
• Template-generated files - resolve in template, regenerate outputs
• Rebase add/add conflicts - per-commit resolution during rebase

Auto-Resolution Script

For automated conflict resolution in CI/CD, use scripts/Resolve-PRConflicts.ps1:

# Resolve conflicts for a PR
pwsh .claude/skills/merge-resolver/scripts/Resolve-PRConflicts.ps1 \
    -PRNumber 123 \
    -BranchName "fix/my-feature" \
    -TargetBranch "main"

Auto-Resolvable Files

The following files are automatically resolved by accepting the target branch version:

Script Output

Returns JSON:

{
  "Success": true,
  "Message": "Successfully resolved conflicts for PR #123",
  "FilesResolved": [".agents/HANDOFF.md"],
  "FilesBlocked": []
}

Exit Codes

Security

ADR-015 compliance:

• Branch name validation (prevents command injection)
• Worktree path validation (prevents path traversal)
• Handles both GitHub Actions runner and local environments

Verification

Success Criteria

Completion Checklist

• All conflicted files staged (git add)
• No UU status in git status --porcelain
• Session log at .agents/sessions/YYYY-MM-DD-session-NN.json
• Session End checklist completed
• Serena memory updated
• Merge commit created
• Branch pushed to origin

Anti-Patterns

Extension Points

Custom Auto-Resolvable Patterns

Add patterns to $script:AutoResolvableFiles in Resolve-PRConflicts.ps1:

$script:AutoResolvableFiles += @(
    'your/custom/path/*',
    'another/pattern/**'
)

Custom Resolution Strategies

Create new entries in references/strategies.md for domain-specific conflicts:

1. Document the conflict pattern
2. Add investigation commands
3. Define resolution priority
4. Provide copy-paste commands

Integration with CI/CD

The script supports GitHub Actions via environment detection:

# In workflow YAML
- name: Resolve conflicts
  env:
    PR_NUMBER: ${{ github.event.pull_request.number }}
    HEAD_REF: ${{ github.head_ref }}
    BASE_REF: ${{ github.base_ref }}
  run: |
    pwsh .claude/skills/merge-resolver/scripts/Resolve-PRConflicts.ps1 \
      -PRNumber "$env:PR_NUMBER" \
      -BranchName "$env:HEAD_REF" \
      -TargetBranch "$env:BASE_REF"

Dry-Run Mode

Use -WhatIf for testing without side effects:

pwsh scripts/Resolve-PRConflicts.ps1 -PRNumber 123 -BranchName "fix/test" -WhatIf

Related

• ADR-015: Security validation for branch names and paths
• SESSION-PROTOCOL.md: Session end requirements (blocking gate)
• strategies.md: Detailed resolution patterns for edge cases
• merge-resolver-session-protocol-gap: Memory documenting root cause analysis