git-commit-signoff

name	git-commit-signoff
description	Use whenever creating, amending, rebasing, squashing, fixing up, or modifying Git commits in this repository. Ensures every commit created or changed by the AI includes a Signed-off-by trailer using Git's built-in signoff mechanism and a Co-Authored-By trailer identifying the AI tool.

Git Commit Sign-off Skill

This repository requires Git commits created or modified by the AI to include:

1. a Signed-off-by trailer; and
2. a Co-Authored-By trailer identifying the AI tool that created or modified the commit.

Always use Git's built-in sign-off mechanism for Signed-off-by instead of manually typing the sign-off trailer.

Core rule

When creating a new commit, always use one of:

git commit -s

git commit --signoff

When committing with an inline message, use:

git commit -s -m "commit message"

Do not create commits with plain git commit unless the commit message already contains a valid Signed-off-by trailer and the user explicitly asked not to amend it.

Every commit created or modified by the AI must also include an AI co-author trailer, for example:

Co-Authored-By: Claude Opus 4.7 <[e-mail]>

Use the actual AI tool name and email identity configured for this repository or requested by the user. Do not invent an AI identity.

Why this matters

git commit -s appends a trailer like:

Signed-off-by: Name <[e-mail]>

The identity comes from Git configuration:

git config user.name
git config user.email

Do not invent or manually write a sign-off identity. Let Git generate it.

The AI co-author trailer makes it clear that an AI tool helped create or modify the commit.

AI co-author identity

Before creating or modifying commits, determine which AI co-author trailer should be used.

If the repository, user, or existing contribution policy specifies an AI co-author identity, use that exact identity.

Examples:

Co-Authored-By: Claude Opus 4.7 <[e-mail]>

Co-Authored-By: ChatGPT <[e-mail]>

If no AI co-author identity is configured or provided, ask the user which AI co-author trailer to use before creating the commit.

Do not guess the AI tool name, version, or email address.

Before committing

Before creating a commit, check what will be committed:

git status --short
git diff --cached

If nothing is staged, either stage the intended files or ask the user what should be included.

When staging changes, prefer explicit paths:

git add path/to/file

Avoid broad staging like this unless the user clearly wants all changes committed:

git add .

Creating a signed-off commit with AI co-author trailer

Use:

git commit -s

or with a message:

git commit -s -m "component: short description"

For multi-line commit messages, include the AI co-author trailer as a commit message paragraph:

git commit -s \
  -m "component: short description" \
  -m "Longer explanation of the change." \
  -m "Co-Authored-By: Claude Opus 4.7 <[e-mail]>"

If using an editor, let git commit -s add the Signed-off-by trailer, then add the AI co-author trailer to the trailer block.

Amending the latest commit

When amending the latest commit, always preserve or add sign-off and preserve or add the AI co-author trailer.

If the message may be edited:

git commit --amend --signoff

If the message should stay unchanged and already contains the correct AI co-author trailer:

git commit --amend --signoff --no-edit

If the latest commit is missing the AI co-author trailer, amend the message and add it:

git commit --amend --signoff

If the latest commit already has a Signed-off-by trailer, --signoff may add another trailer depending on the current identity and message state. Check the final message after amending.

Fixing a commit that missed sign-off or AI co-author

If the latest commit was accidentally created without sign-off, run:

git commit --amend --signoff --no-edit

If the latest commit was accidentally created without the AI co-author trailer, run:

git commit --amend

Then add the correct trailer, for example:

Co-Authored-By: Claude Opus 4.7 <[e-mail]>

Finally verify:

git show -s --format=full

Verifying trailers

After creating or modifying a commit, verify the latest commit contains both required trailers:

git show -s --format=full

or:

git log -1 --pretty=full

Look for lines like:

Signed-off-by: Name <[e-mail]>
Co-Authored-By: Claude Opus 4.7 <[e-mail]>

Rebasing, squashing, fixing up, or rewording

When modifying existing commits through rebase, ensure every resulting commit still has sign-off and AI co-author trailers.

For an interactive rebase:

git rebase -i HEAD~N

If a commit needs sign-off, mark it as edit, then run:

git commit --amend --signoff --no-edit
git rebase --continue

If a commit needs the AI co-author trailer, mark it as reword or edit, then add the correct trailer to the commit message.

Repeat until all edited commits have the required trailers.

If squashing commits, ensure the final squashed commit message contains both:

Signed-off-by: Name <[e-mail]>
Co-Authored-By: Claude Opus 4.7 <[e-mail]>

Prefer finishing the squash, then running:

git commit --amend --signoff

and adding the AI co-author trailer if it is missing.

Force push safety

If a signed-off amend or rebase changes commits that were already pushed, do not use plain force push.

Use:

git push --force-with-lease

Only push when the user has asked to push or has clearly authorized pushing.

Missing Git identity

If Git cannot create the sign-off because user.name or user.email is not configured, stop and report the issue.

Check with:

git config user.name
git config user.email

Suggest configuring them with:

git config user.name "Your Name"
git config user.email "[e-mail]"

For global configuration:

git config --global user.name "Your Name"
git config --global user.email "[e-mail]"

Do not guess the user's identity.

Do not manually type sign-off

Avoid this unless the user explicitly instructs it:

Signed-off-by: Name <[e-mail]>

Prefer:

git commit -s

or:

git commit --amend --signoff

The AI co-author trailer may be typed manually because Git does not generate it automatically.

Commit message guidance

Use concise, conventional commit messages when possible.

Good examples:

io: add vortex file sink test

storage: handle spill writer cleanup

tests: add coverage for vortex sink writes

Avoid vague messages:

fix

update

changes

Final checklist

Before finishing any commit-related task:

1. Confirm the intended files are staged.
2. Create or amend the commit using -s or --signoff.
3. Add the required AI co-author trailer.
4. Verify the latest commit has Signed-off-by.
5. Verify the latest commit has the correct Co-Authored-By trailer for the AI tool.
6. If history was rewritten and the user asked to push, use git push --force-with-lease.
7. Do not remove existing sign-off or co-author trailers unless explicitly requested.