git-worktree-precommit-hook-flutter-failure

Git Worktree Pre-Commit Hook Flutter Failure

Problem

When using git worktree for parallel development, pre-commit hooks that run flutter analyze fail during git commit even though:

• Running flutter analyze directly in the worktree passes with no issues
• Running the pre-commit hook script manually passes
• The hook passes in the main repo checkout

Root Cause

Git sets GIT_DIR, GIT_INDEX_FILE, and GIT_WORK_TREE environment variables during hook execution. In a worktree, GIT_DIR points to .git/worktrees/<name>/ instead of .git/. When flutter analyze internally runs flutter pub get, pub chokes on this worktree-style GIT_DIR path and fails to resolve dependencies.

The failure is invisible when the hook uses 2>/dev/null on stderr — you only see "Resolving dependencies..." then the failure message, with the actual error suppressed.

Context / Trigger Conditions

• Using git worktree add for parallel branch development
• Pre-commit hook runs flutter analyze or dart analyze
• Hook output shows "Resolving dependencies..." then immediately fails
• No actual analysis errors are reported
• The hook uses set -e (exit on error)
• 2>/dev/null may hide the actual failure cause

Diagnosis

Reproduce the exact failure by simulating git's hook environment:

# This will FAIL (simulates hook execution in worktree)
GIT_DIR=/path/to/main/.git/worktrees/<name> \
  flutter analyze --no-fatal-infos 2>/dev/null

# This will PASS (without git env vars)
flutter analyze --no-fatal-infos

Solution

Add unset GIT_DIR GIT_INDEX_FILE GIT_WORK_TREE to the pre-commit hook after all git commands but before any flutter/dart commands.

#!/bin/bash
set -e

cd "$(git rev-parse --show-toplevel)/mobile"

# Git operations (these NEED the git env vars)
STAGED_DART_FILES=$(git diff --cached --name-only --diff-filter=ACM | grep '\.dart$' || true)

if [ -z "$STAGED_DART_FILES" ]; then
    echo "No Dart files staged, skipping checks"
    exit 0
fi

# Unset git env vars BEFORE running flutter/dart commands.
# Git sets these during hook execution, and flutter pub get
# (called internally by flutter analyze) chokes on worktree-style
# GIT_DIR paths.
unset GIT_DIR GIT_INDEX_FILE GIT_WORK_TREE

# Now flutter/dart commands work in both main repo and worktrees
dart format --output=none --set-exit-if-changed lib test
flutter analyze --no-fatal-infos