Tips

Small tips for better experience with lefthook

Local config

Use lefthook-local.yml to overwrite or extend options from the main config. (Don't forget to add this file to .gitignore)

Disable lefthook in CI

When using NPM package lefthook set CI=true in your CI (if it does not set automatically). When CI=true is set lefthook NPM package won't install the hooks in the postinstall script.

Commitlint example

Let's create a bash script to check conventional commit status .lefthook/commit-msg/commitlint.sh:

echo $(head -n1 $1) | npx commitlint --color

Now we can ask lefthook to run our bash script by adding this code to lefthook.yml file:

# lefthook.yml

commit-msg:
  scripts:
    "commitlint.sh":
      runner: bash

When you try to commit git commit -m "haha bad commit text" script commitlint.sh will be executed. Since commit text doesn't match the default config or custom config that you setup for commitlint, the process will be interrupted.

Parallel execution

You can enable parallel execution if you want to speed up your checks. Lets imagine we have the following rules to lint the whole project:

bundle exec rubocop --parallel && \
bundle exec danger && \
yarn eslint --ext .es6 app/assets/javascripts && \
yarn eslint --ext .es6 test/javascripts && \
yarn eslint --ext .es6 plugins/**/assets/javascripts && \
yarn eslint --ext .es6 plugins/**/test/javascripts && \
yarn eslint app/assets/javascripts test/javascripts

Rewrite it in lefthook custom group. We call it lint:

# lefthook.yml

lint:
  parallel: true
  commands:
    rubocop:
      run: bundle exec rubocop --parallel
    danger:
      run: bundle exec danger
    eslint-assets:
      run: yarn eslint --ext .es6 app/assets/javascripts
    eslint-test:
      run: yarn eslint --ext .es6 test/javascripts
    eslint-plugins-assets:
      run: yarn eslint --ext .es6 plugins/**/assets/javascripts
    eslint-plugins-test:
      run: yarn eslint --ext .es6 plugins/**/test/javascripts
    eslint-assets-tests:
      run: yarn eslint app/assets/javascripts test/javascripts

Then call this group directly:

lefthook run lint

Concurrent files overrides

To prevent concurrent problems with read/write files try flock utility.

# lefthook.yml

graphql-schema:
  glob: "{Gemfile.lock,app/graphql/**/*}"
  run: flock webpack/application/typings/graphql-schema.json yarn typings:update && git diff --exit-code --stat HEAD webpack/application/typings
frontend-tests:
  glob: "**/*.js"
  run: flock -s webpack/application/typings/graphql-schema.json yarn test --findRelatedTests {files}
frontend-typings:
  glob: "**/*.js"
  run: flock -s webpack/application/typings/graphql-schema.json yarn run flow focus-check {files}

Capture ARGS from git in the script

Example script for prepare-commit-msg hook:

COMMIT_MSG_FILE=$1
COMMIT_SOURCE=$2
SHA1=$3

# ...

Git LFS support

If git-lfs binary is not installed and not required in your project, LFS hooks won't be executed, and you won't be warned about it.

Lefthook runs LFS hooks internally for the following hooks:

post-checkout
post-commit
post-merge
pre-push

Errors are suppressed if git LFS is not required for the project. You can use LEFTHOOK_VERBOSE ENV to make lefthook show git LFS output.

Pass stdin to a command or script

When you need to read the data from stdin – specify use_stdin: true. This option is good when you write a command or script that receives data from git using stdin (for the pre-push hook, for example).

Using an interactive command or script

When you need to interact with user – specify interactive: true. Lefthook will connect to the current TTY and forward it to your command's or script's stdin.