Generates conventional commit messages from staged changes or a diff.
Git Commit Writer
What this skill does
This skill directs the agent to read a git diff (or a plain description of changes) and produce a well-formed commit message following the Conventional Commits specification. It chooses the right type (feat, fix, chore, docs, refactor, test, style, perf, ci), picks an appropriate scope, writes a concise subject line, and — when the change is large enough to warrant it — adds a descriptive body.
Use this when you want consistent, meaningful commit history without having to remember the format every time.
How to use
Claude Code / Cline
Copy this file to .agents/skills/git-commit-writer/SKILL.md in your project root.
Then ask the agent:
- *"Write a commit message for my staged changes using the Git Commit Writer skill."*
- *"Here's a diff. Use the Git Commit Writer skill to produce a commit message."*
For Claude Code, you can also run git diff --staged first and paste the output into the chat.
Cursor
Add the contents of the "Prompt / Instructions" section below to your .cursorrules file, or paste it into the Cursor AI pane before asking for a commit message.
Codex
Paste the diff into the Codex chat along with the instructions from the section below. Codex works best when you include the full diff rather than a summary.
The Prompt / Instructions for the Agent
When asked to write a commit message, follow these steps:
1. Read the diff. If not provided, ask for git diff --staged output. Understand every file changed.
2. Determine the commit type using these rules:
feat — a new feature or behavior visible to users or callersfix — a bug fixrefactor — code restructuring with no behavior changeperf — performance improvementtest — adding or fixing testsdocs — documentation only (README, comments, etc.)style — formatting, whitespace, lint (no logic change)chore — build scripts, dependencies, toolingci — CI/CD pipeline changes
3. Choose a scope (optional but recommended). The scope is the part of the codebase most affected, in lowercase: auth, api, ui, db, parser, etc. Use the folder name or module name if unsure.
4. Write the subject line (first line of the commit):
- Format:
type(scope): short description
- Max 72 characters
- Use the imperative mood: "add", "fix", "remove" — not "added", "fixing", "removes"
- Do not capitalize the first word after the colon
- Do not end with a period
5. Write the body if the change needs explanation:
- Leave a blank line between subject and body
- Explain *why* the change was made, not *what* (the diff shows what)
- Wrap lines at 72 characters
- Use bullet points for multiple distinct changes
6. Add a footer if applicable:
- Breaking changes:
BREAKING CHANGE: description
- Issue references:
Closes #123 or Fixes #456
7. Output format:
type(scope): short imperative description
Optional body explaining the why behind the change.
Can be multiple paragraphs. Wrap at 72 chars.
Optional footer: Closes #123
If the diff contains multiple unrelated changes, flag this and suggest splitting into separate commits.
Example
Input to Agent:
> "Here's my staged diff. Write a commit message using the Git Commit Writer skill.
>
>
> diff --git a/server/auth.ts b/server/auth.ts
> index 3a1b2c..9f4e5d 100644
> --- a/server/auth.ts
> +++ b/server/auth.ts
> @@ -42,6 +42,12 @@ export async function login(email: string, password: string) {
> const user = await db.users.findOne({ email });
> if (!user) throw new AuthError('User not found');
> +
> + if (user.lockedUntil && user.lockedUntil > new Date()) {
> + throw new AuthError('Account is temporarily locked. Try again later.');
> + }
> +
> const valid = await bcrypt.compare(password, user.passwordHash);
> if (!valid) {
> + await incrementFailedAttempts(user.id);
> throw new AuthError('Invalid password');
> }
>
Output from Agent:
fix(auth): lock accounts after repeated failed login attempts
Adds a check for the `lockedUntil` field before attempting password
comparison. Also increments a failed-attempt counter on each bad
password so the locking mechanism has data to act on.
Notes
- If you paste a large diff with changes spanning many files and concerns, the agent may suggest splitting it. That is intentional behavior — large atomic commits make history harder to read.
- The skill does not run
git commit automatically. It only produces the message text for you to review and use.
- For monorepos, use the package or workspace name as the scope (e.g.,
feat(api-gateway): ...).