worktree-discipline

One global hook, every repo on the machine, no duplication. Companion to worktree-devproxy (which provides the wt new <branch> remedy the hook points at).

The policy

Scope is automatic: the guard only fires in repos carrying a committed .envrc with export DEV_HOST= — the marker every worktree-devproxy onboarded repo already has. Other repos on the machine are untouched (the hook silently delegates), and every future onboarded repo is covered with no extra step.

Install (once per machine)

cp scripts/pre-commit ~/.githooks/pre-commit
chmod +x ~/.githooks/pre-commit
git config --global core.hooksPath ~/.githooks

Design notes (why it's shaped this way)

• Global core.hooksPath, not per-repo hooks. One copy of the policy; updating it is editing one file. Per-repo .githooks copies drift and need a commit in every repo for every policy change.
• Delegation keeps repo-specific hooks alive. Global hooksPath replaces .git/hooks resolution, so the global hook ends by exec-ing the repo's committed .githooks/pre-commit if present (e.g. onsager's migration-sequence check). Repos must NOT set a local core.hooksPath — local config overrides global and would silently drop the guard (watch for repo setup recipes that do this, e.g. a just setup running git config core.hooksPath .githooks).
• Agent detection is CLAUDECODE=1 — set in every Claude Code Bash session. Other agent runtimes can be added to the same test.
• Main-checkout detection: git rev-parse --git-dir equals --git-common-dir only in the primary checkout; in a linked worktree they differ.
• The remedy is in the error message (use: wt new <branch>), so an agent hitting the wall self-corrects without reading docs.

Verify after install

# in an onboarded repo, on main:        expect "blocked"
git commit --allow-empty -m test
# as an agent in the main checkout on a feature branch: expect "blocked"
# in a `wt new` worktree:               expect commit succeeds
# in a repo without .envrc/DEV_HOST:    expect commit succeeds (guard skipped)

Limits

Local-only: nothing stops a git push of an already-existing main commit or a force-push — pair with GitHub branch protection (squash-only PRs) for the remote half. The escape hatch is honor-system by design; the goal is to keep agents on rails, not to be tamper-proof.