Git Hooks: Automate Your Workflow at the Source

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ls .git/hooks/
# applypatch-msg.sample  pre-commit.sample
# commit-msg.sample      pre-push.sample
# post-update.sample     pre-rebase.sample
# pre-applypatch.sample  prepare-commit-msg.sample
# pre-merge-commit.sample update.sample

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chmod +x .git/hooks/pre-commit

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#!/bin/bash
# .git/hooks/pre-commit

# Get staged files
STAGED=$(git diff --cached --name-only --diff-filter=ACM)

# Run linter on staged JS files
JS_FILES=$(echo "$STAGED" | grep '\.js$')
if [ -n "$JS_FILES" ]; then
    echo "Linting JavaScript..."
    npx eslint $JS_FILES
    if [ $? -ne 0 ]; then
        echo "ESLint failed. Fix errors before committing."
        exit 1
    fi
fi

# Run formatter and re-stage
PYTHON_FILES=$(echo "$STAGED" | grep '\.py$')
if [ -n "$PYTHON_FILES" ]; then
    echo "Formatting Python..."
    black $PYTHON_FILES
    git add $PYTHON_FILES
fi

exit 0

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#!/bin/bash
# .git/hooks/commit-msg

MSG_FILE=$1
MSG=$(cat "$MSG_FILE")

# Require conventional commit format
PATTERN="^(feat|fix|docs|style|refactor|test|chore)(\(.+\))?: .{1,50}"

if ! echo "$MSG" | grep -qE "$PATTERN"; then
    echo "Invalid commit message format."
    echo "Expected: type(scope): description"
    echo "Example: feat(auth): add password reset"
    exit 1
fi

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#!/bin/bash
# .git/hooks/pre-push

echo "Running tests before push..."
npm test

if [ $? -ne 0 ]; then
    echo "Tests failed. Push aborted."
    exit 1
fi

# Prevent push to main
BRANCH=$(git rev-parse --abbrev-ref HEAD)
if [ "$BRANCH" = "main" ]; then
    echo "Direct push to main is not allowed."
    echo "Create a pull request instead."
    exit 1
fi

exit 0

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#!/bin/bash
# .git/hooks/post-merge

# Check if package.json changed
CHANGED=$(git diff-tree -r --name-only --no-commit-id ORIG_HEAD HEAD)

if echo "$CHANGED" | grep -q "package.json"; then
    echo "package.json changed. Running npm install..."
    npm install
fi

if echo "$CHANGED" | grep -q "requirements.txt"; then
    echo "requirements.txt changed. Running pip install..."
    pip install -r requirements.txt
fi

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# Store hooks in repo
mkdir .githooks

# Tell Git to use them
git config core.hooksPath .githooks

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# In your setup script
ln -sf ../../.githooks/pre-commit .git/hooks/pre-commit

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// package.json
{
  "husky": {
    "hooks": {
      "pre-commit": "npm run lint",
      "pre-push": "npm test"
    }
  }
}

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# .pre-commit-config.yaml
repos:
  - repo: https://github.com/psf/black
    rev: 23.1.0
    hooks:
      - id: black
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.4.0
    hooks:
      - id: trailing-whitespace
      - id: end-of-file-fixer

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pre-commit install  # Sets up hooks

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# Skip pre-commit and commit-msg
git commit --no-verify -m "WIP: quick fix"

# Skip pre-push
git push --no-verify

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#!/bin/bash
# Prevent committing console.log, debugger, etc.

if git diff --cached | grep -E '(console\.log|debugger|binding\.pry)'; then
    echo "Found debug statements. Remove before committing."
    exit 1
fi

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#!/bin/bash
# Prevent committing files over 5MB

MAX_SIZE=5242880  # 5MB in bytes

for file in $(git diff --cached --name-only); do
    if [ -f "$file" ]; then
        SIZE=$(wc -c < "$file")
        if [ $SIZE -gt $MAX_SIZE ]; then
            echo "File $file is too large ($SIZE bytes)"
            exit 1
        fi
    fi
done

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#!/bin/bash
# post-commit: Update version file

VERSION=$(git describe --tags --always)
echo "$VERSION" > VERSION
git add VERSION
git commit --amend --no-edit --no-verify

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#!/bin/bash
# post-push (via wrapper)

BRANCH=$(git rev-parse --abbrev-ref HEAD)
curl -X POST "https://slack.webhook.url" \
    -d "{\"text\": \"Pushed to $BRANCH\"}"

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#!/bin/bash
# hooks/update - prevent force push to main

REF=$1
OLD=$2
NEW=$3

if [ "$REF" = "refs/heads/main" ]; then
    if ! git merge-base --is-ancestor $OLD $NEW; then
        echo "Force push to main is not allowed."
        exit 1
    fi
fi

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# Make hook verbose
set -x  # At top of script

# Test hook manually
.git/hooks/pre-commit

# Check exit code
echo $?