Universal Changelog Generator with Build Skip Logic

[ssestak]

Universal Detect Changes and Generate Changelog Action

This action detects changes since the last successful build and generates a changelog based on merge commits. It's designed to be universal, handling various edge cases and providing flexible configuration options.

Key Features

• Detects changes between builds using cache-based tracking
• Generates changelog from merge commit messages
• Smart build skipping when no relevant changes detected
• Fallback mechanisms for first runs or cache misses
• Debug mode for troubleshooting

Inputs

Name	Description	Required	Default
depth	Git history depth to fetch	No	100
debug	Enable debug logging	No	false
time_value	Lookback time amount when no previous build found	No	24
time_unit	Lookback time unit (hours/days/weeks/months)	No	hours

Outputs

Name	Description
skip_build	Boolean indicating if build should be skipped
changelog	Generated changelog string from merge commits
merged_branches	List of merged branch names

How It Works

1. Cache Management:

   • Stores the last successful build commit in cache
   • Uses run-number based cache keys
   • Falls back to previous 5 runs if immediate cache miss

2. Change Detection:

   • First attempts to use cached last build commit
   • If cache miss, falls back to time-based detection
   • Checks for merge commits between last build and current HEAD

3. Build Skip Logic:

   • Skips if no new merge commits since last build
   • Always builds on first run or cache miss
   • Uses time window fallback for determining changes

4. Changelog Generation:

   • Extracts messages from merge commits
   • Formats them into a readable changelog
   • Includes list of merged branch names

Edge Cases Handled

1. First Run:

   • No previous cache exists
   • Uses time-based window to find oldest merge commit
   • Generates changelog from all relevant commits

2. Cache Misses:

   • Tries last 5 run numbers sequentially
   • Falls back to time-based detection if no cache hit
   • Ensures continuous operation even after cache purges

3. Rebased History:

   • Detects if cached commit no longer exists
   • Falls back to time-based window
   • Prevents failures due to force pushes

4. No Changes:

   • Properly handles cases with no new merge commits
   • Sets skip_build to true
   • Provides empty changelog

Example Usage

- name: Use Composite Action - Detect changes and get changelog
      id: detect_changes
      uses: futuredapp/.github/.github/actions/universal-detect-changes-and-generate-changelog@main
      with:
        depth: 200
        debug: true
        time_value: "2"
        time_unit: "days"

Debug Mode

When debug: true, the action provides detailed logging:

• Cache key attempts and results
• Git command outputs
• Commit range calculations
• Changelog generation process

This action is designed to be reliable and maintainable, with clear error handling and fallback mechanisms for various edge cases that might occur in real-world CI/CD pipelines.