Git Commit Info

A simple GitHub Action that retrieves commit information (SHA, message, author, date) using an offset from HEAD. This action uses only local git commands and provides detailed commit metadata.

Features

• ✅ Simple offset-based lookup: Get commit info using an offset from HEAD (0 = HEAD, 1 = HEAD~1, etc.)
• ✅ Comprehensive commit info: Retrieves full SHA, short SHA, commit message, author name, author email, and commit date
• ✅ Backwards-only navigation: Always goes backwards in history from HEAD (HEAD~X format)
• ✅ Forgiving input: Negative offsets are accepted but converted to absolute value for convenience
• ✅ Local git commands only: Uses only local git commands (no remote operations)
• ✅ Verbose logging: Optional verbose debug logging for troubleshooting
• ✅ TypeScript implementation: Built with TypeScript for type safety and reliability

Usage

Basic Example - Get Current Commit Info (HEAD)

- name: Get Commit Info
  uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '0'  # 0 means HEAD (default)

This retrieves information about the current HEAD commit and sets outputs:

• sha: Full commit SHA (40 characters)
• short-sha: Short commit SHA (7 characters)
• message: Commit message (first line/subject)
• message-raw: Full commit message (includes all lines, preserves newlines)
• author: Author name
• author-email: Author email address
• date: Commit date (ISO format)
• date-iso: Commit date in ISO 8601 format

Get Previous Commit Info (HEAD~1)

- name: Get Previous Commit Info
  uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '1'  # One commit before HEAD
  id: prev-commit

Get Commit Info with Offset

- name: Get Commit Info
  uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '2'  # Two commits before HEAD
  id: commit-info

- name: Use Commit Info
  run: |
    echo "Commit SHA: ${{ steps.commit-info.outputs.sha }}"
    echo "Short SHA: ${{ steps.commit-info.outputs.short-sha }}"
    echo "Message: ${{ steps.commit-info.outputs.message }}"
    echo "Full Message: ${{ steps.commit-info.outputs.message-raw }}"
    echo "Author: ${{ steps.commit-info.outputs.author }}"

With Verbose Debug Logging

- name: Get Commit Info
  uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '0'
    verbose: true  # Enables detailed debug logging

Using Outputs in Workflow

- name: Checkout code
  uses: actions/checkout@v6
  with:
    fetch-depth: 0  # Full history needed for offsets

- name: Get Commit Info
  uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '1'  # Previous commit
  id: commit-info

- name: Display Commit Info
  run: |
    echo "Full SHA: ${{ steps.commit-info.outputs.sha }}"
    echo "Short SHA: ${{ steps.commit-info.outputs.short-sha }}"
    echo "Message: ${{ steps.commit-info.outputs.message }}"
    echo "Full Message: ${{ steps.commit-info.outputs.message-raw }}"
    echo "Author: ${{ steps.commit-info.outputs.author }} <${{ steps.commit-info.outputs.author-email }}>"
    echo "Date: ${{ steps.commit-info.outputs.date-iso }}"

- name: Use Commit SHA in Another Step
  run: |
    # Use the commit SHA for something
    COMMIT_SHA="${{ steps.commit-info.outputs.sha }}"
    echo "Working with commit: $COMMIT_SHA"

Negative Offset Support (Convenience Feature)

- name: Get Commit Info with Negative Offset
  uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '-1'  # Negative offsets are converted to absolute value (same as 1)

Note: The offset always goes backwards from HEAD. Negative offsets are accepted as a convenience feature - if you accidentally use a negative number, it will be converted to its absolute value. For example, offset: '-1' becomes offset: '1' (both resolve to HEAD~1). You cannot go "forward" in commit history.

Inputs

Input	Description	Required	Default
offset	Offset from HEAD to look up. Always goes backwards in history: 0 = HEAD, 1 = HEAD~1, 2 = HEAD~2, etc. Negative offsets are accepted but converted to absolute value (e.g., -1 becomes 1).	No	'0'
verbose	Enable verbose debug logging. Sets ACTIONS_STEP_DEBUG=true environment variable and enables detailed debug output	No	'false'

Outputs

Output	Description
sha	Full commit SHA (40 characters)
short-sha	Short commit SHA (7 characters)
message	Commit message (first line/subject)
message-raw	Full commit message (includes all lines, preserves newlines)
author	Author name
author-email	Author email address
date	Commit date (ISO format)
date-iso	Commit date in ISO 8601 format

Permissions

No special permissions are required. Typical workflows need contents: read for checkout.

Examples

Get Current Commit Info

- uses: LiquidLogicLabs/git-action-commit-info@v2
  # offset defaults to 0 (HEAD)

Get Previous Commit Info

- uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '1'  # HEAD~1

Get Commit Info for Comparison

- name: Get Previous Commit
  uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '1'
  id: prev-commit

- name: Get Current Commit
  uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '0'
  id: current-commit

- name: Compare Commits
  run: |
    echo "Previous: ${{ steps.prev-commit.outputs.short-sha }} - ${{ steps.prev-commit.outputs.message }}"
    echo "Current: ${{ steps.current-commit.outputs.short-sha }} - ${{ steps.current-commit.outputs.message }}"

Error Handling

If the offset exceeds the commit history, the action will fail with a clear error message:

- name: Get Commit Info (may fail)
  uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '1000'  # Will fail if repository doesn't have 1000 commits
  continue-on-error: true

How It Works

1. Offset Calculation: The action calculates the git reference from the offset (e.g., HEAD~1 for offset 1, HEAD for offset 0)
2. Git Command Execution: Uses git log -1 with a custom format to retrieve all commit information in one call
3. Output Parsing: Parses the git log output and extracts commit metadata
4. Output Setting: Sets all outputs (sha, sha, short-sha, message, author, author-email, date, date-iso) for use in subsequent workflow steps

Offset Behavior

The offset always goes backwards from HEAD in the commit history:

• offset=0: HEAD (current commit)
• offset=1: HEAD~1 (one commit before HEAD)
• offset=2: HEAD~2 (two commits before HEAD)
• offset=3: HEAD~3 (three commits before HEAD)

Negative offsets: Negative offsets are accepted for convenience but are converted to their absolute value:

• offset=-1: Converted to 1 → HEAD~1 (same as offset=1)
• offset=-2: Converted to 2 → HEAD~2 (same as offset=2)

Important: Git doesn't support going "forward" in history. The offset always navigates backwards from HEAD. Negative offsets are provided as a convenience feature - if you accidentally use a negative number, it will still work by converting it to the equivalent positive offset.

Error Handling

The action will fail with clear error messages in the following cases:

• Invalid offset: If the offset is not a valid integer
• Offset exceeds history: If the offset is larger than the number of commits in the repository
• Git command failure: If git commands fail for any other reason

Requirements

• Git must be available in the runner environment (standard in GitHub Actions)
• The repository must have at least one commit
• For offsets greater than 0, fetch-depth: 0 may be required in the checkout step to get full history:

- uses: actions/checkout@v6
  with:
    fetch-depth: 0  # Full history needed for offsets > 0

Logging

Basic Logging (Always Enabled)

The action provides informative logging at each step:

• Offset calculation
• Commit information retrieval
• Summary of retrieved commit info

Verbose Debug Logging

Enable verbose logging by setting verbose: true:

- uses: LiquidLogicLabs/git-action-commit-info@v2
  with:
    offset: '0'
    verbose: true

This enables:

• Detailed debug output via core.debug()
• Sets ACTIONS_STEP_DEBUG=true for GitHub Actions debug logging
• Shows git command outputs and intermediate steps

Security

• The action uses only local git commands (no remote operations)
• No secrets or sensitive data are accessed
• All git commands are executed with proper error handling
• The action validates all inputs before execution

License

This project is licensed under the MIT License.

Contributing

Contributions are welcome! Please see the Development Guide for information on how to contribute.