Git Commit Trailers Skill

Git Commit Trailers

Structured key-value metadata at the end of commit messages. Trailers drive release-please automation, attribution, and issue linking.

When to Use

| Need | Skill | |------|-------| | Trailer lines in commits (this skill) | git-commit-trailers | | Commit message format (type/scope/subject) | git-commit-workflow | | Issue reference keywords (Fixes/Closes/Refs) | github-issue-autodetect | | Release-please config setup | release-please-configuration |

Release-Please Trailers

These trailers directly control version bumps and changelog generation.

BREAKING CHANGE

Triggers a major version bump. Both forms are recognized:

feat(api)!: redesign authentication endpoints

BREAKING CHANGE: /v1/users endpoint removed. Use /v2/users instead.

| Approach | Example | When to Use | |----------|---------|-------------| | ! suffix | feat(api)!: remove endpoint | Short, self-evident breaks | | Footer trailer | BREAKING CHANGE: detailed explanation | Needs migration context | | Both | feat!: subject + BREAKING CHANGE: footer | Maximum clarity |

Both BREAKING CHANGE: and BREAKING-CHANGE: (hyphenated) are recognized.

Release-As

Force a specific version in the next release. Case-insensitive.

git commit --allow-empty -m "chore: release 2.0.0" -m "Release-As: 2.0.0"

| Use Case | Example | |----------|---------| | Initial 1.0.0 from 0.x | Release-As: 1.0.0 | | Calendar versioning | Release-As: 2026.03.0 | | Skip version numbers | Release-As: 3.0.0 |

Multiple Changes in One Commit

A single commit can produce multiple changelog entries via footer messages:

feat: add v4 UUID to crypto

This adds support for v4 UUIDs to the library.

fix(utils): unicode no longer throws exception
  BREAKING-CHANGE: encode method no longer throws.

feat(utils): update encode to support unicode

Additional conventional commit messages must be at the bottom of the commit body.

BEGIN_COMMIT_OVERRIDE

Edit a merged PR body to override its changelog entry. Only works with squash-merge.

BEGIN_COMMIT_OVERRIDE
feat: add ability to override merged commit message

fix: correct typo in error message
END_COMMIT_OVERRIDE

Use when a commit message needs correction after merge without reverting.

Attribution Trailers

| Trailer | Format | When to Use | |---------|--------|-------------| | Co-authored-by | Name <email> | Pair programming, AI-assisted work | | Signed-off-by | Name <email> | DCO compliance (Linux kernel, CNCF projects) | | Reviewed-by | Name <email> | Code review attribution | | Tested-by | Name <email> | Test verification | | Acked-by | Name <email> | Acknowledgment without full review |

Issue references (Fixes #N, Closes #N, Refs #N) are also trailers — see github-issue-autodetect skill.

Decision Tree

What trailers does this commit need?
├─ Breaking API change? → BREAKING CHANGE: <description>
├─ Force specific version? → Release-As: x.x.x
├─ AI-assisted code? → Co-authored-by: Claude <noreply@anthropic.com>
├─ DCO-required project? → Signed-off-by: Name <email>
├─ Fixes/closes an issue? → See github-issue-autodetect
└─ None of the above → No trailers needed

Detect DCO requirement:

git log -20 --format='%B' | git interpret-trailers --parse | grep -c "Signed-off-by"

Detecting Project Conventions

Scan recent commits to discover what trailers a project uses:

# Parse all trailers from recent commits
git log -20 --format='%B' | git interpret-trailers --parse

# List unique trailer types
git log -20 --format='%B' | git interpret-trailers --parse | sort -u -t: -k1,1

# Count trailer usage
git log -50 --format='%B' | git interpret-trailers --parse | cut -d: -f1 | sort | uniq -c | sort -rn

Always match existing project conventions before adding new trailer types.

Composing Trailers with `git interpret-trailers`

# Add a trailer to a message
echo "feat(auth): add OAuth2" | git interpret-trailers \
  --trailer "Co-authored-by: Claude <noreply@anthropic.com>"

# Add multiple trailers
echo "feat(auth): add OAuth2" | git interpret-trailers \
  --trailer "Co-authored-by: Claude <noreply@anthropic.com>" \
  --trailer "Signed-off-by: Dev <dev@example.com>"

# Parse trailers from last commit
git log -1 --format='%B' | git interpret-trailers --parse

Agentic Optimizations

| Context | Command | |---------|---------| | Parse last commit trailers | git log -1 --format='%B' \| git interpret-trailers --parse | | Check DCO convention | git log -20 --format='%B' \| git interpret-trailers --parse \| grep -c Signed-off-by | | Detect trailer patterns | git log -20 --format='%B' \| git interpret-trailers --parse \| sort -u -t: -k1,1 | | Count trailer usage | git log -50 --format='%B' \| git interpret-trailers --parse \| cut -d: -f1 \| sort \| uniq -c \| sort -rn |

Agent Skills: Git Commit Trailers

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