By name: dco description: > Recover from missing DCO sign-off on commits. Handles the single-commit amend, older-commit recovery via interactive rebase or cherry-pick, and explains the Probot DCO check that blocks PRs without sign-off. Use when a PR fails the DCO check, when a commit needs a Signed-off-by trailer added retroactively, or when sign-off was forgotten during rebase / cherry-pick / amend. allowed-tools: Bash, Read, Edit
DCO Sign-off Recovery
All commits in this repo must carry a Signed-off-by: trailer (Developer Certificate of Origin). The Probot DCO check on PRs blocks merge until every commit is signed.
The standard way to add it is with --signoff at commit time. This skill handles the cases where that was missed.
Case 1: Last commit only
git commit --amend --signoff -S --no-edit
git push --force-with-lease
--force-with-lease is preferred over plain --force — it refuses if someone else has pushed to the branch since you last fetched.
Case 2: Older commit on the same branch
Find the commit hash of the oldest unsigned commit:
git log --pretty='%h %s %(trailers:key=Signed-off-by,valueonly)' origin/main..HEAD
# Any line with an empty trailing field is unsigned
Then interactively rebase from one commit before that:
git rebase -i <parent-of-unsigned-commit>
# In the editor, change `pick` to `edit` for each unsigned commit
# Save and exit; the rebase stops at each `edit` line so you can amend
For each commit in the rebase, replace it with a signed version:
git commit --amend --signoff -S --no-edit
git rebase --continue
When done, force-push:
git push --force-with-lease
Case 3: Cherry-pick / merge brought in unsigned commits
Cherry-pick with sign-off baked in:
git cherry-pick --signoff <sha>
If you already cherry-picked without it, fall back to Case 1 or Case 2 above.
Verifying the whole branch
Before pushing, verify every commit ahead of origin/main has both DCO and GPG:
git log --format='%G? %(trailers:key=Signed-off-by,valueonly,separator=%x20) %h %s' origin/main..HEAD
Each line must start with G or U (good GPG signature) AND carry a non-empty Signed-off-by value before the SHA. Codes N / B / E need investigation. See .claude/rules/commit-workflow.md for the canonical signing policy.
What the Probot DCO check looks for
The check passes when every commit message includes a Signed-off-by: Name <email> trailer matching the commit author's email. The --signoff (or -s) flag adds this trailer automatically using your user.name and user.email git config.
A failing DCO check on a PR will show a "Details" link explaining which commits are missing sign-off.