Git hook scripts are useful for identifying simple issues before submission to code review. We run our hooks on every commit to automatically point out issues in code such as missing semicolons, trailing whitespace, and debug statements. By pointing these issues out before code review, this allows a code reviewer to focus on the architecture of a change while not wasting time with trivial style nitpicks.

As we created more libraries and projects we recognized that sharing our pre-commit hooks across projects is painful. We copied and pasted unwieldy bash scripts from project to project and had to manually change the hooks to work for different project structures.

We believe that you should always use the best industry standard linters. Some of the best linters are written in languages that you do not use in your project or have installed on your machine. For example scss-lint is a linter for SCSS written in Ruby. If you’re writing a project in node you should be able to use scss-lint as a pre-commit hook without adding a Gemfile to your project or understanding how to get scss-lint installed.

We built pre-commit to solve our hook issues. It is a multi-language package manager for pre-commit hooks. You specify a list of hooks you want and pre-commit manages the installation and execution of any hook written in any language before every commit. pre-commit is specifically designed to not require root access. If one of your developers doesn’t have node installed but modifies a JavaScript file, pre-commit automatically handles downloading and building node to run eslint without root.

Before you can run hooks, you need to have the pre-commit package manager installed.

Using pip:

pip install pre-commit

Non-administrative installation:

• to upgrade: run again, to uninstall: pass uninstall to python
• does not work on platforms without symlink support (windows)

curl https://pre-commit.com/install-local.py | python -

In a python project, add the following to your requirements.txt (or requirements-dev.txt):

pre-commit

Using homebrew:

brew install pre-commit

Using conda (via conda-forge):

conda install -c conda-forge pre-commit

Quick start ¶

1. Install pre-commit ¶

• follow the install instructions above
• pre-commit --version should show you what version you're using

$ pre-commit --version
pre-commit 1.18.1

2. Add a pre-commit configuration ¶

• create a file named .pre-commit-config.yaml
• you can generate a very basic configuration using pre-commit sample-config
• the full set of options for the configuration are listed below
• this example uses a formatter for python code, however pre-commit works for any programming language
• other supported hooks are available

repos:
-   repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v2.3.0
    hooks:
    -   id: check-yaml
    -   id: end-of-file-fixer
    -   id: trailing-whitespace
-   repo: https://github.com/psf/black
    rev: 19.3b0
    hooks:
    -   id: black

3. Install the git hook scripts ¶

• run pre-commit install to set up the git hook scripts

$ pre-commit install
pre-commit installed at .git/hooks/pre-commit

• now pre-commit will run automatically on git commit!

4. (optional) Run against all the files ¶

• it's usually a good idea to run the hooks against all of the files when adding new hooks (usually pre-commit will only run on the changed files during git hooks)

$ pre-commit run --all-files
[INFO] Initializing environment for https://github.com/pre-commit/pre-commit-hooks.
[INFO] Initializing environment for https://github.com/psf/black.
[INFO] Installing environment for https://github.com/pre-commit/pre-commit-hooks.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
[INFO] Installing environment for https://github.com/psf/black.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
Check Yaml...............................................................Passed
Fix End of Files.........................................................Passed
Trim Trailing Whitespace.................................................Failed
hookid: trailing-whitespace

Files were modified by this hook. Additional output:

Fixing sample.py

black....................................................................Passed

• oops! looks like I had some trailing whitespace
• consider running that in CI too

Once you have pre-commit installed, adding pre-commit plugins to your project is done with the .pre-commit-config.yaml configuration file.

Add a file called .pre-commit-config.yaml to the root of your project. The pre-commit config file describes what repositories and hooks are installed.

.pre-commit-config.yaml - top level ¶

new in 1.0.0: The default configuration file top-level was changed from a list to a map. If you're using an old version of pre-commit, the top-level list is the same as the value of repos. If you'd like to migrate to the new configuration format, run pre-commit migrate-config to automatically migrate your configuration.

default_language_version:
    python: python3.7

default_stages: [commit, push]

A sample top-level:

exclude: '^$'
fail_fast: false
repos:
-   ...

.pre-commit-config.yaml - repos ¶

The repository mapping tells pre-commit where to get the code for the hook from.

A sample repository with all defaults present:

repos:
-   repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v1.2.3
    hooks:
    -   ...

.pre-commit-config.yaml - hooks ¶

The hook mapping configures which hook from the repository is used and allows for customization. All optional keys will receive their default from the repository's configuration.

One example of a complete configuration:

repos:
-   repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v1.2.3
    hooks:
    -   id: trailing-whitespace

This configuration says to download the pre-commit-hooks project and run its trailing-whitespace hook.

Updating hooks automatically ¶

You can update your hooks to the latest version automatically by running pre-commit autoupdate. This will bring the hooks to the latest tag on the master branch.

Run pre-commit install to install pre-commit into your git hooks. pre-commit will now run on every commit. Every time you clone a project using pre-commit running pre-commit install should always be the first thing you do.

If you want to manually run all pre-commit hooks on a repository, run pre-commit run --all-files. To run individual hooks use pre-commit run <hook_id>.

The first time pre-commit runs on a file it will automatically download, install, and run the hook. Note that running a hook for the first time may be slow. For example: If the machine does not have node installed, pre-commit will download and build a copy of node.

$ pre-commit install
pre-commit installed at /home/asottile/workspace/pytest/.git/hooks/pre-commit
$ git commit -m "Add super awesome feature"
black....................................................................Passed
blacken-docs.........................................(no files to check)Skipped
Trim Trailing Whitespace.................................................Passed
Fix End of Files.........................................................Passed
Check Yaml...........................................(no files to check)Skipped
Debug Statements (Python)................................................Passed
Flake8...................................................................Passed
Reorder python imports...................................................Passed
pyupgrade................................................................Passed
rst ``code`` is two backticks........................(no files to check)Skipped
rst..................................................(no files to check)Skipped
changelog filenames..................................(no files to check)Skipped
[master 146c6c2c] Add super awesome feature
 1 file changed, 1 insertion(+)

pre-commit currently supports hooks written in many languages. As long as your git repo is an installable package (gem, npm, pypi, etc.) or exposes an executable, it can be used with pre-commit. Each git repo can support as many languages/hooks as you want.

The hook must exit nonzero on failure or modify files in the working directory (since 0.6.3).

A git repo containing pre-commit plugins must contain a .pre-commit-hooks.yaml file that tells pre-commit:

For example:

-   id: trailing-whitespace
    name: Trim Trailing Whitespace
    description: This hook trims trailing whitespace.
    entry: trailing-whitespace-fixer
    language: python
    types: [text]

new in 0.12.0: Prior to 0.12.0 the file was hooks.yaml (now .pre-commit-hooks.yaml). For backwards compatibility it is suggested to provide both files or suggest users use pre-commit>=0.12.0.

Developing hooks interactively ¶

Since the repo property of .pre-commit-config.yaml can refer to anything that git clone ... understands, it's often useful to point it at a local directory while developing hooks.

pre-commit try-repo streamlines this process by enabling a quick way to try out a repository. Here's how one might work interactively:

new in 1.14.0: a commit is no longer necessary to try-repo on a local directory. pre-commit will clone any uncommitted changes.

~/work/hook-repo $ git checkout origin/master -b feature

# ... make some changes

# new in 1.14.0: a commit is no longer necessary for `try-repo`

# In another terminal or tab

~/work/other-repo $ pre-commit try-repo ../hook-repo foo --verbose --all-files
===============================================================================
Using config:
===============================================================================
repos:
-   repo: ../hook-repo
    rev: 84f01ac09fcd8610824f9626a590b83cfae9bcbd
    hooks:
    -   id: foo
===============================================================================
[INFO] Initializing environment for ../hook-repo.
[foo] Foo................................................................Passed
hookid: foo

Hello from foo hook!

Supported languages ¶

• docker
• docker_image
• fail
• golang
• node
• python
• python_venv
• ruby
• rust
• swift
• pcre
• pygrep
• script
• system

docker ¶

new in 0.10.0

The hook repository must have a Dockerfile. It will be installed via docker build ..

Running Docker hooks requires a running Docker engine on your host. For configuring Docker hooks, your entry should correspond to an executable inside the Docker container, and will be used to override the default container entrypoint. Your Docker CMD will not run when pre-commit passes a file list as arguments to the run container command. Docker allows you to use any language that's not supported by pre-commit as a builtin.

Support: docker hooks are known to work on any system which has a working docker executable. It has been tested on linux and macOS. Hooks that are run via boot2docker are known to be unable to make modifications to files.

See this repository for an example Docker-based hook.

docker_image ¶

new in 0.18.0

A more lightweight approach to docker hooks. The docker_image "language" uses existing docker images to provide hook executables.

docker_image hooks can be conveniently configured as local hooks.

The entry specifies the docker tag to use. If an image has an ENTRYPOINT defined, nothing special is needed to hook up the executable. If the container does not specify an ENTRYPOINT or you want to change the entrypoint you can specify it as well in your entry.

For example:

-   id: dockerfile-provides-entrypoint
    name: ...
    language: docker_image
    entry: my.registry.example.com/docker-image-1:latest
-   id: dockerfile-no-entrypoint-1
    name: ...
    language: docker_image
    entry: --entrypoint my-exe my.registry.example.com/docker-image-2:latest
# Alternative equivalent solution
-   id: dockerfile-no-entrypoint-2
    name: ...
    language: docker_image
    entry: my.registry.example.com/docker-image-3:latest my-exe

fail ¶

new in 1.11.0

A lightweight language to forbid files by filename. The fail language is especially useful for local hooks.

The entry will be printed when the hook fails. It is suggested to provide a brief description for name and more verbose fix instructions in entry.

Here's an example which prevents any file except those ending with .rst from being added to the changelog directory:

-   repo: local
    hooks:
    -   id: changelogs-rst
        name: changelogs must be rst
        entry: changelog filenames must end in .rst
        language: fail
        files: 'changelog/.*(?<!\.rst)$'

golang ¶

new in 0.12.0

The hook repository must contain go source code. It will be installed via go get ./.... pre-commit will create an isolated GOPATH for each hook and the entry should match an executable which will get installed into the GOPATH's bin directory.

Support: golang hooks are known to work on any system which has go installed. It has been tested on linux, macOS, and windows.

node ¶

The hook repository must have a package.json. It will be installed via npm install .. The installed package will provide an executable that will match the entry – usually through bin in package.json.

Support: node hooks work without any system-level dependencies. It has been tested on linux and macOS and may work under cygwin.

new in 1.5.0: windows is now supported for node hooks. Currently python3 only due to a bug in cpython.

python ¶

The hook repository must have a setup.py. It will be installed via pip install .. The installed package will provide an executable that will match the entry – usually through console_scripts or scripts in setup.py.

Support: python hooks work without any system-level dependencies. It has been tested on linux, macOS, windows, and cygwin.

python_venv ¶

new in 1.9.0

An alternate implementation of the python language which uses the python 3 venv module. On many systems you need to additionally install the python3-venv system package to use this language. This is otherwise a drop-in replacement for the python language for situations where virtualenv may not work.

Support: python hooks work without any system-level dependencies. It has been tested on linux, macOS, windows, and cygwin. Only python3 environments can be created with this language.

ruby ¶

The hook repository must have a *.gemspec. It will be installed via gem build *.gemspec && gem install *.gem. The installed package will produce an executable that will match the entry – usually through executables in your gemspec.

Support: ruby hooks work without any system-level dependencies. It has been tested on linux and macOS and may work under cygwin.

rust ¶

new in 1.10.0

Rust hooks are installed using the system installation of Cargo, Rust's official package manager.

Hook repositories must have a Cargo.toml file which produces at least one binary (example), whose name should match the entry definition for your hook. The repo will be installed via cargo install --bins (with the binaries stored in your pre-commit cache, not polluting your user-level Cargo installations).

When specifying additional_dependencies for Rust, you can use the syntax {package_name}:{package_version} to specify a new library dependency (used to build your hook repo), or the special syntax cli:{package_name}:{package_version} for a CLI dependency (built separately, with binaries made available for use by hooks).

Support: Rust hooks currently require a pre-existing Rust installation. It has been tested on linux, Windows, and macOS.

swift ¶

new in 0.11.0

The hook repository must have a Package.swift. It will be installed via swift build -c release. The entry should match an executable created by building the repository.

Support: swift hooks are known to work on any system which has swift installed. It has been tested on linux and macOS.

pcre ¶

deprecated: the pcre language will be removed in a later version. Use pygrep hooks instead (usually a drop-in replacement).

"Perl Compatible Regular Expressions" – pcre hooks are a quick way to write a simple hook which prevents commits by file matching. Specify the regex as the entry.

macos does not ship with a functioning grep -P so you'll need brew install grep for pcre hooks to function.

Support: pcre hooks work on any system which has a functioning grep -P (or in the case of macOS: ggrep -P). It has been tested on linux, macOS, windows, and cygwin.

pygrep ¶

new in 1.2.0

A cross-platform python implementation of grep – pygrep hooks are a quick way to write a simple hook which prevents commits by file matching. Specify the regex as the entry. The entry may be any python regular expression. For case insensitive regexes you can apply the (?i) flag as the start of your entry, or use args: [-i].

new in 1.8.0: For multiline matches, use args: [--multiline].

Support: pygrep hooks are supported on all platforms which pre-commit runs on.

script ¶

Script hooks provide a way to write simple scripts which validate files. The entry should be a path relative to the root of the hook repository.

This hook type will not be given a virtual environment to work with – if it needs additional dependencies the consumer must install them manually.

Support: the support of script hooks depend on the scripts themselves.

system ¶

System hooks provide a way to write hooks for system-level executables which don't have a supported language above (or have special environment requirements that don't allow them to run in isolation such as pylint).

This hook type will not be given a virtual environment to work with – if it needs additional dependencies the consumer must install them manually.

Support: the support of system hooks depend on the executables.

All pre-commit commands take the following options:

• --color {auto,always,never}: whether to use color in output. Defaults to auto. new in 1.18.0: can be overridden by using PRE_COMMIT_COLOR={auto,always,never} or disabled using TERM=dumb.
• -c CONFIG, --config CONFIG: path to alternate config file
• -h, --help: show help and available options.

pre-commit autoupdate [options] ¶

Auto-update pre-commit config to the latest repos' versions.

Options:

• --bleeding-edge: update to the bleeding edge of master instead of the latest tagged version (the default behaviour).
• --repo REPO: new in 1.4.1: Only update this repository. new in 1.7.0: This option may be specified multiple times.

pre-commit clean [options] ¶

Clean out cached pre-commit files.

Options: (no additional options)

pre-commit gc [options] ¶

new in 1.14.0

Clean unused cached repos.

pre-commit keeps a cache of installed hook repositories which grows over time. This command can be run periodically to clean out unused repos from the cache directory.

Options: (no additional options)

pre-commit init-templatedir DIRECTORY [options] ¶

new in 1.18.0

Install hook script in a directory intended for use with git config init.templateDir.

Options:

• -t {pre-commit,pre-push,prepare-commit-msg,commit-msg}, --hook-type {pre-commit,pre-push,prepare-commit-msg,commit-msg}: which hook type to install.

Some example useful invocations:

git config --global init.templateDir ~/.git-template
pre-commit init-templatedir ~/.git-template

Now whenever a repository is cloned or created, it will have the hooks set up already!

pre-commit install [options] ¶

Install the pre-commit script.

Options:

• -f, --overwrite: Replace any existing git hooks with the pre-commit script.
• --install-hooks: Also install environments for all available hooks now (rather than when they are first executed). See pre-commit install-hooks.
• -t {pre-commit,pre-push,prepare-commit-msg,commit-msg}, --hook-type {pre-commit,pre-push,prepare-commit-msg,commit-msg}: Specify which hook type to install.
• --allow-missing-config: Hook scripts will permit a missing configuration file.

Some example useful invocations:

• pre-commit install: Default invocation. Installs the pre-commit script alongside any existing git hooks.
• pre-commit install --install-hooks --overwrite: Idempotently replaces existing git hook scripts with pre-commit, and also installs hook environments.

pre-commit install-hooks [options] ¶

Install all missing environments for the available hooks. Unless this command or install --install-hooks is executed, each hook's environment is created the first time the hook is called.

Each hook is initialized in a separate environment appropriate to the language the hook is written in. See supported languages.

This command does not install the pre-commit script. To install the script along with the hook environments in one command, use pre-commit install --install hooks.

Options: (no additional options)

pre-commit migrate-config [options] ¶

new in 1.0.0

Migrate list configuration to the new map configuration format.

Options: (no additional options)

pre-commit run [hook-id] [options] ¶

Run hooks.

Options:

• [hook-id]: specify a single hook-id to run only that hook.
• -a, --all-files: run on all the files in the repo.
• --files [FILES [FILES ...]]: specific filenames to run hooks on.
• --source SOURCE + --origin ORIGIN: run against the files changed between SOURCE...ORIGIN in git.
• --show-diff-on-failure: new in 0.13.4: when hooks fail, run git diff directly afterward.
• -v, --verbose: produce hook output independent of success. Include hook ids in output.

Some example useful invocations:

• pre-commit run: this is what pre-commit runs by default when committing. This will run all hooks against currently staged files.
• pre-commit run --all-files: run all the hooks against all the files. This is a useful invocation if you are using pre-commit in CI.
• pre-commit run flake8: run the flake8 hook against all staged files.
• git ls-files -- '*.py' | xargs pre-commit run --files: run all hooks against all *.py files in the repository.
• pre-commit run --source HEAD^^^ --origin HEAD: run against the files that have changed between HEAD^^^ and HEAD. This form is useful when leveraged in a pre-receive hook.

pre-commit sample-config [options] ¶

Produce a sample .pre-commit-config.yaml.

Options: (no additional options)

pre-commit try-repo REPO [options] ¶

new in 1.3.0

Try the hooks in a repository, useful for developing new hooks. try-repo can also be used for testing out a repository before adding it to your configuration. try-repo prints a configuration it generates based on the remote hook repository before running the hooks.

Options:

• REPO: required clonable hooks repository. Can be a local path on disk.
• --ref REF: Manually select a ref to run against, otherwise the HEAD revision will be used.
• pre-commit try-repo also supports all available options for pre-commit run.

Some example useful invocations:

• pre-commit try-repo https://github.com/pre-commit/pre-commit-hooks: runs all the hooks in the latest revision of pre-commit/pre-commit-hooks.
• pre-commit try-repo ../path/to/repo: run all the hooks in a repository on disk.
• pre-commit try-repo ../pre-commit-hooks flake8: run only the flake8 hook configured in a local ../pre-commit-hooks repository.
• See pre-commit run for more useful run invocations which are also supported by pre-commit try-repo.

pre-commit uninstall [options] ¶

Uninstall the pre-commit script.

Options:

• -t {pre-commit,pre-push,prepare-commit-msg,commit-msg}, --hook-type {pre-commit,pre-push,prepare-commit-msg,commit-msg}: which hook type to uninstall.

Running in migration mode ¶

By default, if you have existing hooks pre-commit install will install in a migration mode which runs both your existing hooks and hooks for pre-commit. To disable this behavior, simply pass -f / --overwrite to the install command. If you decide not to use pre-commit, pre-commit uninstall will restore your hooks to the state prior to installation.

Temporarily disabling hooks ¶

Not all hooks are perfect so sometimes you may need to skip execution of one or more hooks. pre-commit solves this by querying a SKIP environment variable. The SKIP environment variable is a comma separated list of hook ids. This allows you to skip a single hook instead of --no-verifying the entire commit.

$ SKIP=flake8 git commit -m "foo"

pre-commit during commits ¶

Running hooks on unstaged changes can lead to both false-positives and false-negatives during committing. pre-commit only runs on the staged contents of files by temporarily saving the contents of your files at commit time and stashing the unstaged changes while running hooks.

pre-commit during merges ¶

The biggest gripe we’ve had in the past with pre-commit hooks was during merge conflict resolution. When working on very large projects a merge often results in hundreds of committed files. I shouldn’t need to run hooks on all of these files that I didn’t even touch! This often led to running commit with --no-verify and allowed introduction of real bugs that hooks could have caught.

pre-commit solves this by only running hooks on files that conflict or were manually edited during conflict resolution. This also includes files which were automatically merged by git. Git isn't perfect and this can often catch implicit conflicts (such as with removed python imports).

pre-commit during push ¶

new in 0.3.5: pre-commit can be used to manage pre-push hooks. Simply pre-commit install --hook-type pre-push.

pre-commit for commit messages ¶

new in 0.15.4: pre-commit can be used to manage commit-msg hooks. Simply pre-commit install --hook-type commit-msg.

commit-msg hooks can be configured by setting stages: [commit-msg]. commit-msg hooks will be passed a single filename -- this file contains the current contents of the commit message which can be validated. If a hook exits nonzero, the commit will be aborted.

new in 1.16.0: pre-commit can be used to manage prepare-commit-msg hooks. Simply pre-commit install --hook-type prepare-commit-msg.

prepare-commit-msg hooks can be used to create dynamic templates for commit messages. prepare-commit-msg hooks can be configured by setting stages: [prepare-commit-msg]. prepare-commit-msg hooks will be passed a single filename -- this file contains any initial commit message (e.g. from git commit -m "..." or a template) and can be modified by the hook before the editor is shown. A hook may want to check for GIT_EDITOR=: as this indicates that no editor will be launched. If a hook exits nonzero, the commit will be aborted.

Confining hooks to run at certain stages ¶

Since the default_stages top level configuration property of the .pre-commit-config.yaml file is set to all stages by default, when installing hooks using the -t/--hook-type option (see pre-commit install [options]), all hooks will be installed by default to run at the stage defined through that option. for instance, pre-commit install --hook-type pre-push will install by default all hooks to run at the push stage.

Hooks can however be confined to a stage by setting the stages property in your .pre-commit-config.yaml. The stages property is an array and can contain any of commit, push, prepare-commit-msg, commit-msg and manual.

If you do not want to have hooks installed by default on the stage passed during a pre-commit install --hook-type ..., please set the default_stages top level configuration property to the desired stages, also as an array.

new in 1.8.0: An additional manual stage is available for one off execution that won't run in any hook context. This special stage is useful for taking advantage of pre-commit's cross-platform / cross-language package management without running it on every commit. Hooks confied to stages: [manual] can be executed by running pre-commit run --hook-stage manual <hookid>.

Passing arguments to hooks ¶

Sometimes hooks require arguments to run correctly. You can pass static arguments by specifying the args property in your .pre-commit-config.yaml as follows:

-   repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v1.2.3
    hooks:
    -   id: flake8
        args: [--max-line-length=131]

This will pass --max-line-length=131 to flake8.

Arguments pattern in hooks ¶

If you are writing your own custom hook, your hook should expect to receive the args value and then a list of staged files.

For example, assuming a .pre-commit-config.yaml:

-   repo: https://github.com/path/to/your/hook/repo
    rev: badf00ddeadbeef
    hooks:
    -   id: my-hook-script-id
        args: [--myarg1=1, --myarg1=2]

When you next run pre-commit, your script will be called:

path/to/script-or-system-exe --myarg1=1 --myarg1=2 dir/file1 dir/file2 file3

If the args property is empty or not defined, your script will be called:

path/to/script-or-system-exe dir/file1 dir/file2 file3

Repository local hooks ¶

Repository-local hooks are useful when:

• The scripts are tightly coupled to the repository and it makes sense to distribute the hook scripts with the repository.
• Hooks require state that is only present in a built artifact of your repository (such as your app's virtualenv for pylint).
• The official repository for a linter doesn't have the pre-commit metadata.

You can configure repository-local hooks by specifying the repo as the sentinel local.

new in 0.13.0: local hooks can use any language which supports additional_dependencies or docker_image / fail / pcre / pygrep / script / system. This enables you to install things which previously would require a trivial mirror repository.

A local hook must define id, name, language, entry, and files / types as specified under Creating new hooks.

Here's an example configuration with a few local hooks:

-   repo: local
    hooks:
    -   id: pylint
        name: pylint
        entry: python -m pylint.__main__
        language: system
        types: [python]
    -   id: check-x
        name: Check X
        entry: ./bin/check-x.sh
        language: script
        files: \.x$
    -   id: scss-lint
        name: scss-lint
        entry: scss-lint
        language: ruby
        language_version: 2.1.5
        types: [scss]
        additional_dependencies: ['scss_lint:0.52.0']

meta hooks ¶

new in 1.4.0

pre-commit provides several hooks which are useful for checking the pre-commit configuration itself. These can be enabled using repo: meta.

-   repo: meta
    hooks:
    -   id: ...

The currently available meta hooks:

automatically enabling pre-commit on repositories ¶

new in 1.18.0

pre-commit init-templatedir can be used to set up a skeleton for git's init.templateDir option. This means that any newly cloned repository will automatically have the hooks set up without the need to run pre-commit install.

To configure, first set git's init.templateDir -- in this example I'm using ~/.git-template as my template directory.

$ git config --global init.templateDir ~/.git-template
$ pre-commit init-templatedir ~/.git-template
pre-commit installed at /home/asottile/.git-template/hooks/pre-commit

Now whenever you clone a pre-commit enabled repo, the hooks will already be set up!

$ git clone -q [email protected]:asottile/pyupgrade
$ cd pyupgrade
$ git commit --allow-empty -m 'Hello world!'
Check docstring is first.............................(no files to check)Skipped
Check Yaml...........................................(no files to check)Skipped
Debug Statements (Python)............................(no files to check)Skipped
...

init-templatedir uses the --allow-missing-config option from pre-commit install so repos without a config will be skipped:

$ git init sample
Initialized empty Git repository in /tmp/sample/.git/
$ cd sample
$ git commit --allow-empty -m 'Initial commit'
`.pre-commit-config.yaml` config file not found. Skipping `pre-commit`.
[master (root-commit) d1b39c1] Initial commit

Filtering files with types ¶

new in 0.15.0

Filtering with types provides several advantages over traditional filtering with files.

• no error-prone regular expressions
• files can be matched by their shebang (even when extensionless)
• symlinks / submodules can be easily ignored

types is specified per hook as an array of tags. The tags are discovered through a set of heuristics by the identify library. identify was chosen as it is a small portable pure python library.

Some of the common tags you'll find from identify:

• file
• symlink
• directory - in the context of pre-commit this will be a submodule
• executable - whether the file has the executable bit set
• text - whether the file looks like a text file
• binary - whether the file looks like a binary file
• tags by extension / naming convention
• tags by shebang (#!)

To discover the type of any file on disk, you can use identify's cli:

$ identify-cli setup.py
["file", "non-executable", "python", "text"]
$ identify-cli some-random-file
["file", "non-executable", "text"]
$ identify-cli --filename-only some-random-file; echo $?
1

If a file extension you use is not supported, please submit a pull request!

types and files are evaluated with AND when filtering. Tags within types are also evaluated using AND.

For example:

    files: ^foo/
    types: [file, python]

will match a file foo/1.py but will not match setup.py.

Files can also be matched by shebang. With types: python, an exe starting with #!/usr/bin/env python3 will also be matched.

As with files and exclude, you can also exclude types if necessary using exclude_types.

If you'd like to use types with compatibility for older versions here is a guide to ensuring compatibility.

Regular expressions ¶

The patterns for files and exclude are python regular expressions and are matched with re.search.

As such, you can use any of the features that python regexes support.

If you find that your regular expression is becoming unwieldy due to a long list of excluded / included things, you may find a verbose regular expression useful. One can enable this with yaml's multiline literals and the (?x) regex flag.

# ...
    -   id: my-hook
        exclude: >
            (?x)^(
                path/to/file1.py|
                path/to/file2.py|
                path/to/file3.py
            )$

Overriding language version ¶

Sometimes you only want to run the hooks on a specific version of the language. For each language, they default to using the system installed language (So for example if I’m running python2.7 and a hook specifies python, pre-commit will run the hook using python2.7). Sometimes you don’t want the default system installed version so you can override this on a per-hook basis by setting the language_version.

-   repo: https://github.com/pre-commit/mirrors-scss-lint
    rev: v0.54.0
    hooks:
    -   id: scss-lint
        language_version: 2.1.5

This tells pre-commit to use ruby 2.1.5 to run the scss-lint hook.

Valid values for specific languages are listed below:

• python: Whatever system installed python interpreters you have. The value of this argument is passed as the -p to virtualenv.
  • new in 1.4.3: on windows the pep394 name will be translated into a py launcher call for portability. So continue to use names like python3 (py -3) or python3.6 (py -3.6) even on windows.
• node: See nodeenv.
• ruby: See ruby-build.

new in 1.14.0: you can now set default_language_version at the top level in your configuration to control the default versions across all hooks of a language.

default_language_version:
    # force all unspecified python hooks to run python3
    python: python3
    # force all unspecified ruby hooks to run ruby 2.1.5
    ruby: 2.1.5

Usage in continuous integration ¶

pre-commit can also be used as a tool for continuous integration. For instance, adding pre-commit run --all-files as a CI step will ensure everything stays in tip-top shape. To check only files which have changed, which may be faster, use something like git diff-tree --no-commit-id --name-only -r $REVISION | xargs pre-commit run --files.

Managing CI Caches ¶

pre-commit by default places its repository store in ~/.cache/pre-commit -- this can be configured in two ways:

• PRE_COMMIT_HOME: if set, pre-commit will use that location instead.
• XDG_CACHE_HOME: if set, pre-commit will use $XDG_CACHE_HOME/pre-commit following the XDG Base Directory Specification.

travis-ci example ¶

cache:
  directories:
  - $HOME/.cache/pre-commit

appveyor example ¶

cache:
- '%USERPROFILE%\.cache\pre-commit'

azure pipelines example ¶

note: azure pipelines uses immutable caches so the python version and .pre-commit-config.yaml hash must be included in the cache key. for a repository template, see [[email protected]].

jobs:
- job: precommit

  # ...

  variables:
    PRE_COMMIT_HOME: $(Pipeline.Workspace)/pre-commit-cache

  steps:

  # ...

  - script: echo "##vso[task.setvariable variable=PY]$(python -VV)"
  - task: [email protected]
    inputs:
      key: pre-commit | .pre-commit-config.yaml | "$(PY)"
      path: $(PRE_COMMIT_HOME)

github actions example ¶

see the official pre-commit github action

like azure pipelines, github actions also uses immutable caches:

    - name: set PY
      run: echo "::set-env name=PY::$(python -VV | sha256sum | cut -d' ' -f1)"
    - uses: actions/[email protected]
      with:
        path: ~/.cache/pre-commit
        key: pre-commit|${{ env.PY }}|${{ hashFiles('.pre-commit-config.yaml') }}

Usage with tox ¶

tox is useful for configuring test / CI tools such as pre-commit. One feature of tox>=2 is it will clear environment variables such that tests are more reproducible. Under some conditions, pre-commit requires a few environment variables and so they must be whitelisted.

When cloning repos over ssh (repo: [email protected]:...), git requires the SSH_AUTH_SOCK variable and will otherwise fail:

[INFO] Initializing environment for [email protected]:pre-commit/pre-commit-hooks.
An unexpected error has occurred: CalledProcessError: Command: ('/usr/bin/git', 'clone', '--no-checkout', '[email protected]:pre-commit/pre-commit-hooks', '/home/asottile/.cache/pre-commit/repofdkwkq_v')
Return code: 128
Expected return code: 0
Output: (none)
Errors:
    Cloning into '/home/asottile/.cache/pre-commit/repofdkwkq_v'...
    Permission denied (publickey).
    fatal: Could not read from remote repository.

    Please make sure you have the correct access rights
    and the repository exists.


Check the log at /home/asottile/.cache/pre-commit/pre-commit.log

Add the following to your tox testenv:

[testenv]
passenv = SSH_AUTH_SOCK

Likewise, when cloning repos over http / https (repo: https://github.com:...), you might be working behind a corporate http(s) proxy server, in which case git requires the http_proxy, https_proxy and no_proxy variables to be set, or the clone may fail:

[testenv]
passenv = http_proxy https_proxy no_proxy

Using the latest version for a repository ¶

pre-commit configuration aims to give a repeatable and fast experience and therefore intentionally doesn't provide facilities for "unpinned latest version" for hook repositories.

Instead, pre-commit provides tools to make it easy to upgrade to the latest versions with pre-commit autoupdate. If you need the absolute latest version of a hook (instead of the latest tagged version), pass the --bleeding-edge parameter to autoupdate.

pre-commit assumes that the value of rev is an immutable ref (such as a tag or SHA) and will cache based on that. Using a branch name (or HEAD) for the value of rev is not supported and will only represent the state of that mutable ref at the time of hook installation (and will NOT update automatically).

We’re looking to grow the project and get more contributors especially to support more languages/versions. We’d also like to get the .pre-commit-hooks.yaml files added to popular linters without maintaining forks / mirrors.

Feel free to submit bug reports, pull requests, and feature requests.

Contributors ¶

• website by Molly Finkle
• created by Anthony Sottile
• core developers: Ken Struys, Chris Kuehl
• framework contributors
• core hook contributors
• and users like you!