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 unicodeAdditional 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_OVERRIDEUse 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 neededDetect 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 -rnAlways 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 --parseAgentic 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` |