pre-push-format-guard

name	pre-push-format-guard
description	Set up a git pre-push hook that rejects pushes when code isn't formatted. Detects the repo's formatter and writes a check-only hook.
user-invocable	true
allowed-tools	Bash Glob Grep Read Write

Format Guard

Set up a git pre-push hook that runs the project's code formatter in check-only mode, rejecting the push if any file is not properly formatted.

Steps

1. Detect the formatter. Inspect the repo for formatter config files, dependency manifests, and tool configs (e.g. .prettierrc, biome.json, pyproject.toml, Cargo.toml, go.mod, deno.json, etc.). Use your knowledge of the ecosystem to determine which formatter the project uses and what the correct check-only command is.

2. If no formatter is detected, tell the user you couldn't find one and stop. Don't guess.

3. Check for an existing pre-push hook. If .git/hooks/pre-push already exists, show the user its contents and ask how to proceed — don't overwrite silently.

4. Write the hook. Create .git/hooks/pre-push as a shell script that:

   • Captures the formatter's check command output (stdout and stderr)
   • On success: prints nothing — the hook should be completely silent when everything is fine
   • On failure: prints the captured output followed by a clear message explaining what happened and how to fix it
   • Keeps it minimal — just the check, no extra logic

5. Make it executable. chmod +x .git/hooks/pre-push

6. Report. Tell the user what formatter was detected, what check command the hook runs, and how to bypass it (git push --no-verify) if needed.