affiance

A tool to manage and configure Git hooks

Inspired by and shamelessly ported from Overcommit.

In addition to supporting a wide variety of hooks that can be used across multiple repositories, you can also define hooks specific to a repository, but, unlike regular Git hooks, are stored in source control. You can also easily add your existing hook scripts without writing any Javascript code.

• Definition
• Requirements
  • Dependencies
• Limitations
• Installation
• Usage
• Configuration
  • Hook Options
  • Hook Categories
  • Plugin Directory
  • Concurrency
  • Node Module Mode
  • Signature Verification
• Built-In Hooks
  • CommitMsg
  • PostCheckout
  • PostCommit
  • PostMerge
  • PostRewrite
  • PreCommit
  • PrePush
  • PreRebase
• Repo-Specific Hooks
  • Adding Existing Git Hooks
• Security
• Contributing
• Community
• Changelog
• License

Definition

affiance

v. to pledge by promise of marriage; betroth. n. trust; confidence; reliance.

Requirements

This project aims to support the following node versions runtimes on *nix machines:

• Node 4+

Windows is not yet supported, but could be with your help!

Dependencies

Some of the hooks have third-party dependencies. For example, to lint your STYL files, you're going to need the stylint module.

Depending on the hooks you enable/disable for your repository, you'll need to ensure your development environment already has those dependencies installed. Most hooks will display a warning if a required executable isn't available.

Limitations

Affiance does not currently support git-worktree.

Installation

affiance is installed via npm. It is strongly recommended that your environment support running npm install without requiring sudo privileges. Using a Node version manager like nvm can help here.

Once you have an environment that allows you to install packages without sudo, you can run the following command to make affiance available globally:

Global installation

npm install -g affiance

If Affiance is installed globally, the cli binary will be in your PATH. In any repo existing repo, run the following to install the affiance.

cd ~/important-project
affiance install
affiance sign # See Security section below for explanation

Repo specific installation

Like most npm modules, Affiance can (and usually should) be installed locally. In a team context where multiple repos are involved, using global modules is not sustainable as each repo may have different requirements. The caveat is that if Affiance is not installed globally, the binary from the ./node_modules/.bin directory must be used to run the various installation commands. Affiance assumes this is the default, so all error messages from affiance will encourage you to run the command from the local binary instead of the global binary. Affiance also opinionatedly assumes that other node modules will be installed locally. If you want to use the global binary, change the requiredExecutable property of the hook in question.

mkdir important-project
cd important-project
git init
npm init # Create a package.json and name the module
npm install affiance --save-dev # Save `affiance` to devDependencies in package.json
./node_modules/.bin/affiance install
./node_modules/.bin/affiance sign # See Security section below for explanation

See the Security section of the documentation to understand why affiance sign is necessary after installing hooks for the first time.

After running affiance install, any existing hooks for your repository which Affiance will replace will be backed up. You can restore everything to the way it was by running affiance uninstall.

Usage

Once you've installed the hooks via affiance install, they will automatically run when the appropriate hook is triggered.

The affiance executable supports the following subcommands:

Subcommand | Description -------------------|---------------------------------------------------- install | Install Affiance hooks in a repository uninstall | Remove Affiance hooks from a repository version | Show version of affiance -h / -help | Show subcommand flag documentation

Skipping Hooks

Sometimes a hook will report an error that for one reason or another you'll want to ignore. To prevent these errors from blocking your commit, you can include the name of the relevant hook in the SKIP environment variable, e.g.

SKIP=EsLint git commit

If you would prefer to specify a whitelist of hooks rather than a blacklist, use the ONLY environment variable instead.

ONLY=EsLint git commit

Use this feature sparingly, as there is no point to having the hook in the first place if you're just going to ignore it. If you want to ensure a hook is never skipped, set the required option to true in its configuration. If you attempt to skip it, you'll see a warning telling you that the hook is required, and the hook will still run.

Disabling Affiance

If you have scripts that execute git commands where you don't want Affiance hooks to run, you can disable Affiance entirely by setting the AFFIANCE_DISABLE environment variable.

AFFIANCE_DISABLE=1 ./my-custom-script

Configuration

Affiance provides a flexible configuration system that allows you to tailor the built-in hooks to suit your workflow. All configuration specific to a repository is stored in .affiance.yml in the top-level directory of the repository.

When writing your own configuration, it will automatically extend the default configuration, so you only need to specify your configuration with respect to the default. In order to enable/disable hooks, you can add the following to your repo-specific configuration file:

PreCommit:
  RuboCop:
    enabled: true
    command: ['bundle', 'exec', 'rubocop'] # Invoke within Bundler context

Hook Options

Individual hooks expose both built-in configuration options as well as their own custom options unique to each hook. The following table lists all built-in configuration options:

Option | Description ----------------------------------------|-------------------------------------- enabled | If false, this hook will never be run required | If true, this hook cannot be skipped via the SKIP environment variable quiet | If true, this hook does not display any output unless it warns/fails description | Message displayed while hook is running. requires_files | If true, this hook runs only if files that are applicable to it have been modified. See include and exclude for how to specify applicable files. include | File paths or glob patterns of files that apply to this hook. The hook will only run on the applicable files when they have been modified. Note that the concept of modified varies for different types of hooks. By default, include matches every file until you specify a list of patterns. exclude | File paths or glob patterns of files that do not apply to this hook. This is used to exclude any files that would have been matched by include. problemOnUnmodifiedLine | How to treat errors reported on lines that weren't modified during the action captured by this hook (e.g. for pre-commit hooks, warnings/errors reported on lines that were not staged with git add may not be warnings/errors you care about). Valid values are report: report errors/warnings as-is regardless of line location (default); warn: report errors as warnings if they are on lines you didn't modify; and ignore: don't display errors/warnings at all if they are on lines you didn't modify (ignore is not recommended). ignoreMessagePattern | A string pattern to use to completely ignore certain messages for the hook. This is useful to work around the lack of configuration options in some linters. For example the pattern '[Vv]ariable "_.*" is assigned to but never read' will filter out linting errors for unused variables that start with _. onFail | Change the status of a failed hook to warn or pass. This allows you to treat failures as warnings or potentially ignore them entirely, but you should use caution when doing so as you might be hiding important information. onWarn | Similar to on_fail, change the status of a hook that returns a warning status to either pass (you wish to silence warnings entirely) or fail (you wish to treat all warnings as errors). requiredExecutable | Name of an executable that must exist in order for the hook to run. If this is a path (e.g. ./bin/ruby), ensures that the executable file exists at the given location relative to the repository root. Otherwise, if it just the name of an executable (e.g. ruby) checks if the executable can be found in one of the directories in the PATH environment variable. Set this to a specific path if you want to always use an executable that is stored in your repository. (e.g. RubyGems bin stubs, Node.js binaries, etc.) requiredLibrary/requiredLibraries | List of Ruby libraries to load with Kernel.require before the hook runs. This is specifically for hooks that integrate with external Ruby libraries. command | Array of arguments to use as the command. How each hook uses this is different, but it allows hooks to change the context with which they run. For example, you can change the command to be ['bundle', 'exec', 'rubocop'] instead of just rubocop so that you can use the gem versions specified in your local Gemfile.lock. This defaults to the name of the required_executable. flags | Array of arguments to append to the command. This is useful for customizing the behavior of a tool. It's also useful when a newer version of a tool removes/renames existing flags, so you can update the flags via your .affiance.yml instead of waiting for an upstream fix in Affiance. env | Hash of environment variables the hook should be run with. This is intended to be used as a last resort when an executable a hook runs is configured only via an environment variable. Any pre-existing environment variables with the same names as ones defined in env will have their original values restored after the hook runs. NOTE: Currently, only strings are accepted values. Boolean values will raise an error. WARNING: If you set the same environment variable for multiple hooks and you've enabled parallel hook runs, since the environment is shared across all threads you could accidentally have these separate hooks trample on each other. In this case, you should disable parallelization for the hook using the parallelize option. parallelize | Whether to allow this hook to be run concurrently with other hooks. Disable this if the hook requires access to a shared resource that other hooks may also access and modify (e.g. files, the git index, process environment variables, etc). processors | The number of processing units to reserve for this hook. This does not reserve CPUs, but indicates that out of the total number of possible concurrent hooks allowed by the global concurrency option, this hook requires the specified number. Thus in the typical case where concurrency is set to the number of available cores (default), and you have a hook that executes an application which itself creates 2 threads (or is otherwise scheduled on 2 cores), you can indicate that Affiance should allocate 2 processors to the hook. Ideally this means your hooks won't put undue load on your available cores. installCommand | Command the user can run to install the required_executable (or alternately the specified required_libraries). This is intended for documentation purposes, as Affiance does not install software on your behalf since there are too many edge cases where such behavior would result in incorrectly configured installations (e.g. installing a Python package in the global package space instead of in a virtual environment). skipFileCheckout | Whether to skip this hook for file checkouts (e.g. git checkout some-ref -- file). Only applicable to PostCheckout hooks.

In addition to the built-in configuration options, each hook can expose its own unique configuration options. The AuthorEmail hook, for example, allows you to customize the regex used to check commit author emails via the pattern option—useful if you want to enforce that developers use a company email address for their commits. This provides incredible flexibility for hook authors as you can make your hooks sufficiently generic and then customize them on a per-project basis.

The ALL Hook

Within a hook category, there is a special type of hook configuration that applies to all hooks in the category. This configuration looks like a normal hook configuration, except it has the name ALL:

PreCommit:
  ALL:
    problemOnUnmodifiedLine: warn
    requiresFiles: true
    required: false
    quiet: false

  SomeHook:
    enabled: true

  ...

The ALL configuration is useful for when you want to DRY up your configuration, or when you want to apply changes across an entire category of hooks.

Note that array configuration options (like include/exclude) in the special ALL hook section are not merged with individual hook configurations if custom ones are defined for the hook. Any custom configuration option for include/exclude will replace the ALL hook's configuration. If you want to have a global list of default exclusions and extend them with a custom list, you can use YAML references, e.g.

PreCommit:
  ALL:
    exclude: &defaultExcludes
      - 'node_modules/**/*'
      - 'vendor/**/*'
  MyHook:
    exclude:
      - *defaultExcludes
      - 'another/directory/in/addition/to/default/excludes/**/*'

Again, you can consult the default configuration for detailed examples of how the ALL hook can be used.

Plugin Directory

You can change the directory that project-specific hooks are loaded from via the plugin_directory option. The default directory is .git-hooks.

Quiet Hook Runs

If you prefer to have your hooks be completely silent unless there is a problem, you can set the top-level quiet option to true. Note that if you have many hooks or slow hooks this may not be desirable, as you don't get visual feedback indicating the general progress of the hook run.

Concurrency

Affiance runs hooks in parallel by default, with a number of concurrent workers equal to the number of logical cores on your machine. If you know your particular set of hooks would benefit from higher/lower number of workers, you can adjust the global concurrency option. You can define single-operator mathematical expressions, e.g. %{processors} * 2, or %{processors} / 2.

concurrency: '%{processors} / 4'

Note that individual hooks can specify the number of processors they require with the processors hook option. See the hook options section for more details.

Node Module Mode

Affiance assumes that all node modules hooks depend on will be installed locally. So by default, binaries are invoked using the binary directory of locally installed modules (usually ./node_modules/.bin). However, if you would like to use the global version of dependent modules for all node bases linters, you can set the nodeModuleMode to global. When in global mode, affiance will not attempt to verify requiredLibraries and will assume the necessary binaries are in the PATH and will be invoked using the normal binary name.

nodeModuleMode: 'global'

Note, when in global mode, affiance will use the globalRequiredExecutable configuration to run the hook and the globalInstallCommand to output install instructions. You can always specify a specific behavior for a hook by specifying a command option or overriding the configurations above.

Signature Verification

You can disable manual verification of signatures by setting verify_signatures to false. See the Security section for more information on this option and what exactly it controls.

Built-In Hooks

Currently, Affiance supports the following hooks out of the box—simply enable them in your .affiance.yml.

Note: Hooks with a * are enabled by default.

CommitMsg

commit-msg hooks are run against every commit message you write before a commit is created. A failed hook prevents a commit from being created. These hooks are useful for enforcing policies on your commit messages, e.g. ensuring a task ID is included for tracking purposes, or ensuring your commit messages follow proper formatting guidelines.

• *CapitalizedSubject
• *EmptyMessage

PostCheckout

post-checkout hooks run after a successful git checkout, or in other words any time your HEAD changes or a file is explicitly checked out.

• NpmInstall

PostCommit

post-commit hooks run after a commit is successfully created. A hook failing in this case does not prevent the commit since it has already occurred; however, it can be used to alert the user to some issue.

• NpmInstall

PostMerge

post-merge hooks run after a git merge executes successfully with no merge conflicts. A hook failing in this case does not prevent the merge since it has already occurred; however, it can be used to alert the user to some issue.

• NpmInstall

PostRewrite

post-rewrite hooks run after a commit is modified by a git commit --amend or git rebase. A hook failing in this case does not prevent the rewrite since it has already occurred; however, it can be used to alert the user to some issue.

• NpmInstall

PreCommit

pre-commit hooks are run after git commit is executed, but before the commit message editor is displayed. If a hook fails, the commit will not be created. These hooks are ideal for syntax checkers, linters, and other checks that you want to run before you allow a commit to even be created.

WARNING: pre-commit hooks cannot have side effects

pre-commit hooks currently do not support hooks with side effects (such as modifying files and adding them to the index with git add). This is a consequence of Affiance's pre-commit hook stashing behavior to ensure hooks are run against only the changes you are about to commit.

Without Affiance, the proper way to write a pre-commit hook would be to extract the staged changes into temporary files and lint those files instead of whatever contents are in your working tree (as you don't want unstaged changes to taint your results). Affiance takes care of this for you, but to do it in a generalized way introduces this limitation.

• CoffeeLint
• EsLint
• *MergeConflicts
• MochaOnly
• Spectral
• StylusLint
• TsLint

PrePush

pre-push hooks are run during git push, after remote refs have been updated but before any objects have been transferred. If a hook fails, the push is aborted.

• Mocha

PreRebase

pre-rebase hooks are run during git rebase, before any commits are rebased. If a hook fails, the rebase is aborted.

• MergedCommits

Repo-Specific hooks

Out of the box, affiance comes with a set of hooks that enforce a variety of styles and lints. However, some hooks only make sense in the context of a specific repository.

At Lever, for example, we have a number of simple checks that we run against our code to catch common errors. For example, since we use coffeescript in development, we want to make sure all requires do not specify the file extension of .coffee because those won't work when the code is compiled to javascript.

Inside our repository, we can add the file .git-hooks/pre-commit/NoRequireCoffee.js in order to automatically check our that requires don't specify .coffee:

fse =  require 'fse'
PreCommitBase = require 'affiance/lib/hook/pre-commit/Base'

module.exports = class NoRequireCoffee extends PreCommitBase
  run: ->
    errors = []
    @applicableFiles().forEach (filePath) ->
      if fse.readFileSync(filePath, 'utf8').match /require.*\.coffee/g
        errors.push "#{filePath}: has a require that specifies .coffee"
      end
    end

    return ['fail', errors.join("\n")] if errors.length
    return 'pass'

The corresponding configuration for this hook would look like:

PreCommit:
  NoRequireCoffee:
    enabled: true
    description: 'Check for requires that specify the coffee extension'
    include: '**/*.coffee'

Adding Existing Git Hooks

You might already have hook scripts written which you'd like to integrate with Affiance right away. To make this easy, Affiance allows you to include your hook script in your configuration without writing any Javascript code. For example:

PostCheckout:
  CustomScript:
    enabled: true
    requiredExecutable: './bin/custom-script'

So long as a command is given (either by specifying the command option directly or specifying required_executable) a special hook is created that executes the command and appends any arguments and standard input stream that would have been passed to the regular hook. The hook passes or fails based on the exit status of the command.

Security

While Affiance can make managing Git hooks easier and more convenient, this convenience can come at a cost of being less secure.

Since installing Affiance hooks will allow arbitrary plugin code in your repository to be executed, you expose yourself to an attack where checking out code from a third party can result in malicious code being executed on your system.

As an example, consider the situation where you have an open source project. An attacker could submit a pull request which adds a post-checkout hook that executes some malicious code. When you fetch and checkout this pull request, the post-checkout hook will be run on your machine, along with the malicious code that you just checked out.

Affiance attempts to address this problem by storing a signature of your configuration and all hook plugin code since the last time it ran. When the signature changes, a warning is displayed alerting you to which plugins have changed. It is then up to you to manually verify that the changes are not malicious, and then continue running the hooks.

The signature is derived from the contents of the plugin's source code itself and any configuration for the plugin. Thus a change to the plugin's source code or your local repo's .affiance.yml file could result in a signature change.

Disabling Signature Checking

In typical usage, your plugins usually don't change too often, so this warning should not become a nuisance. However, users who work within proprietary repositories where all developers who can push changes to the repository already have a minimum security clearance may wish to disable this check.

While not recommended, you can disable signature verification by setting verifySignatures to false in your .affiance.yml file.

Regardless of whether you have verifySignatures disabled for your project, if you are running Affiance for the first time you will need to sign your configuration with affiance sign. This needs to happen once so Affiance can record in your local git repo's configuration (outside of source control) that you intend to enable/disable verification. This way if someone else changes verifySignatures you'll be asked to confirm the change.

Contributing

I love contributions to Affiance, be they bug reports, feature ideas, or pull requests. See our guidelines for contributing to best ensure your thoughts, ideas, or code get merged.

Community

All major discussion surrounding Affiance happens on the GitHub issues list.

You can also follow @l8on on Twitter. Maybe someday the community will be big enough to warrant its own Twitter account.

Changelog

If you're interested in seeing the changes and bug fixes between each version of affiance, read the Affiance Changelog.

License

This project is released under the MIT license.