Introduction

Gitlint is a git commit message linter written in python: it checks your commit messages for style.

Great for use as a commit-msg git hook or as part of your gating script in a CI pipeline (e.g. Jenkins).

Note

Gitlint support for Windows is experimental, and there are some known issues.

Also, gitlint is not the only git commit message linter out there, if you are looking for an alternative written in a different language, have a look at fit-commit (Ruby), node-commit-msg (Node.js) or commitlint (Node.js).

Important

Gitlint will soon be dropping support for Python 2.7 and Python 3.5 as they have reached End-Of-Life.

Features

Getting Started

Installation

# Pip is recommended to install the latest version
pip install gitlint

# macOS
brew install gitlint
sudo port install gitlint  # alternative

# Ubuntu
apt-get install gitlint

# Docker: https://hub.docker.com/r/jorisroovers/gitlint
docker run --ulimit nofile=1024 -v $(pwd):/repo jorisroovers/gitlint
# NOTE: --ulimit is required to work around a limitation in Docker
# Details: https://github.com/jorisroovers/gitlint/issues/129

Usage

# Check the last commit message
gitlint
# Alternatively, pipe a commit message to gitlint:
cat examples/commit-message-1 | gitlint
# or
git log -1 --pretty=%B | gitlint
# Or read the commit-msg from a file, like so:
gitlint --msg-filename examples/commit-message-2
# Lint all commits in your repo
gitlint --commits HEAD

# To install a gitlint as a commit-msg git hook:
gitlint install-hook

Output example:

$ cat examples/commit-message-2 | gitlint
1: T1 Title exceeds max length (134>80): "This is the title of a commit message that    is over 80 characters and contains hard tabs and trailing whitespace and the word wiping  "
1: T2 Title has trailing whitespace: "This is the title of a commit message that    is over 80 characters and contains hard tabs and trailing whitespace and the word wiping  "
1: T4 Title contains hard tab characters (\t): "This is the title of a commit message that  is over 80 characters and contains hard tabs and trailing whitespace and the word wiping  "
2: B4 Second line is not empty: "This line should not contain text"
3: B1 Line exceeds max length (125>80): "Lines typically need to have   a max length, meaning that they can't exceed a preset number of characters, usually 80 or 120. "
3: B2 Line has trailing whitespace: "Lines typically need to have   a max length, meaning that they can't exceed a preset number of characters, usually 80 or 120. "
3: B3 Line contains hard tab characters (\t): "Lines typically need to have     a max length, meaning that they can't exceed a preset number of characters, usually 80 or 120. "

Note

The returned exit code equals the number of errors found. Some exit codes are special.

Configuration

For in-depth documentation of general and rule-specific configuration options, have a look at the Configuration and Rules pages.

Short example .gitlint file (full reference):

[general]
# Ignore certain rules (comma-separated list), you can reference them by
# their id or by their full name
ignore=body-is-missing,T3

# Ignore any data send to gitlint via stdin
ignore-stdin=true

# Configure title-max-length rule, set title length to 80 (72 = default)
[title-max-length]
line-length=80

# You can also reference rules by their id (B1 = body-max-line-length)
[B1]
line-length=123

Example use of flags:

# Change gitlint's verbosity.
$ gitlint -v
# Ignore certain rules
$ gitlint --ignore body-is-missing,T3
# Enable debug mode
$ gitlint --debug
# Load user-defined rules (see http://jorisroovers.github.io/gitlint/user_defined_rules)
$ gitlint --extra-path /home/joe/mygitlint_rules

Other commands and variations:

$ gitlint --help
Usage: gitlint [OPTIONS] COMMAND [ARGS]...

  Git lint tool, checks your git commit messages for styling issues

  Documentation: http://jorisroovers.github.io/gitlint

Options:
  --target DIRECTORY       Path of the target git repository. [default:
                           current working directory]
  -C, --config FILE        Config file location [default: .gitlint]
  -c TEXT                  Config flags in format <rule>.<option>=<value>
                           (e.g.: -c T1.line-length=80). Flag can be used
                           multiple times to set multiple config values.
  --commits TEXT           The range of commits to lint. [default: HEAD]
  -e, --extra-path PATH    Path to a directory or python module with extra
                           user-defined rules
  --ignore TEXT            Ignore rules (comma-separated by id or name).
  --contrib TEXT           Contrib rules to enable (comma-separated by id or
                           name).
  --msg-filename FILENAME  Path to a file containing a commit-msg.
  --ignore-stdin           Ignore any stdin data. Useful for running in CI
                           server.
  --staged                 Read staged commit meta-info from the local
                           repository.
  -v, --verbose            Verbosity, more v's for more verbose output (e.g.:
                           -v, -vv, -vvv). [default: -vvv]
  -s, --silent             Silent mode (no output). Takes precedence over -v,
                           -vv, -vvv.
  -d, --debug              Enable debugging output.
  --version                Show the version and exit.
  --help                   Show this message and exit.

Commands:
  generate-config  Generates a sample gitlint config file.
  install-hook     Install gitlint as a git commit-msg hook.
  lint             Lints a git repository [default command]
  uninstall-hook   Uninstall gitlint commit-msg hook.

  When no COMMAND is specified, gitlint defaults to 'gitlint lint'.

Using gitlint as a commit-msg hook

Introduced in gitlint v0.4.0

You can also install gitlint as a git commit-msg hook so that gitlint checks your commit messages automatically after each commit.

gitlint install-hook
# To remove the hook
gitlint uninstall-hook

Important

Gitlint cannot work together with an existing hook. If you already have a .git/hooks/commit-msg file in your local repository, gitlint will refuse to install the commit-msg hook. Gitlint will also only uninstall unmodified commit-msg hooks that were installed by gitlint. If you're looking to use gitlint in conjunction with other hooks, you should consider using gitlint with pre-commit.

Using gitlint through pre-commit

gitlint can be configured as a plugin for the pre-commit git hooks framework. Simply add the configuration to your .pre-commit-config.yaml:

-   repo: https://github.com/jorisroovers/gitlint
    rev:  # Fill in a tag / sha here
    hooks:
    -   id: gitlint

You then need to install the pre-commit hook like so:

pre-commit install --hook-type commit-msg

Important

It's important that you run pre-commit install --hook-type commit-msg, even if you've already used pre-commit install before. pre-commit install does not install commit-msg hooks by default!

To manually trigger gitlint using pre-commit for your last commit message, use the following command:

pre-commit run gitlint --hook-stage commit-msg --commit-msg-filename .git/COMMIT_EDITMSG

In case you want to change gitlint's behavior, you should either use a .gitlint file (see Configuration) or modify the gitlint invocation in your .pre-commit-config.yaml file like so:

-   repo: https://github.com/jorisroovers/gitlint
    rev:  # Fill in a tag / sha here
    hooks:
    -   id: gitlint
        stages: [commit-msg]
        entry: gitlint
        args: [--contrib=CT1, --msg-filename]

Using gitlint in a CI environment

By default, when just running gitlint without additional parameters, gitlint lints the last commit in the current working directory.

This makes it easy to use gitlint in a CI environment (Jenkins, TravisCI, Github Actions, pre-commit, CircleCI, Gitlab, etc). In fact, this is exactly what we do ourselves: on every commit, we run gitlint as part of our CI checks. This will cause the build to fail when we submit a bad commit message.

Alternatively, gitlint will also lint any commit message that you feed it via stdin like so:

# lint the last commit message
git log -1 --pretty=%B | gitlint
# lint a specific commit: 62c0519
git log -1 --pretty=%B 62c0519 | gitlint

Note that gitlint requires that you specify --pretty=%B (=only print the log message, not the metadata), future versions of gitlint might fix this and not require the --pretty argument.

Linting a range of commits

Introduced in gitlint v0.9.0 (experimental in v0.8.0)

Gitlint allows users to lint a number of commits at once like so:

# Lint a specific commit range:
gitlint --commits "019cf40...d6bc75a"
# You can also use git's special references:
gitlint --commits "origin..HEAD"
# Or specify a single specific commit in refspec format, like so:
gitlint --commits "019cf40^...019cf40"

The --commits flag takes a single refspec argument or commit range. Basically, any range that is understood by git rev-list as a single argument will work.

For cases where the --commits option doesn't provide the flexibility you need, you can always use a simple shell script to lint an arbitrary set of commits, like shown in the example below.

#!/bin/sh

for commit in $(git rev-list master); do
    commit_msg=$(git log -1 --pretty=%B $commit)
    echo "$commit"
    echo "$commit_msg" | gitlint
    echo "--------"
done

Note

One downside to this approach is that you invoke gitlint once per commit vs. once per set of commits. This means you'll incur the gitlint startup time once per commit, making this approach rather slow if you want to lint a large set of commits. Always use --commits if you can to avoid this performance penalty.

Merge, fixup, squash and revert commits

Introduced in gitlint v0.7.0 (merge), v0.9.0 (fixup, squash) and v0.13.0 (revert)

Gitlint ignores merge, revert, fixup and squash commits by default.

For merge and revert commits, the rationale for ignoring them is that most users keep git's default messages for these commits (i.e Merge/Revert "[original commit message]"). Often times these commit messages are also auto-generated through tools like github. These default/auto-generated commit messages tend to cause gitlint violations. For example, a common case is that "Merge:" being auto-prepended triggers a title-max-length violation. Most users don't want this, so we disable linting on Merge and Revert commits by default.

For squash and fixup commits, the rationale is that these are temporary commits that will be squashed into a different commit, and hence the commit messages for these commits are very short-lived and not intended to make it into the final commit history. In addition, by prepending "fixup!" or "squash!" to your commit message, certain gitlint rules might be violated (e.g. title-max-length) which is often undesirable.

In case you do want to lint these commit messages, you can disable this behavior by setting the general ignore-merge-commits, ignore-revert-commits, ignore-fixup-commits or ignore-squash-commits option to false using one of the various ways to configure gitlint.

Ignoring commits

Introduced in gitlint v0.10.0

You can configure gitlint to ignore specific commits or parts of a commit.

One way to do this, is to by adding a gitline-ignore line to your commit message.

If you have a case where you want to ignore a certain type of commits all-together, you can use gitlint's ignore rules. Here's an example gitlint file that configures gitlint to ignore rules title-max-length and body-min-length for all commits with a title starting with "Release".

[ignore-by-title]
# Match commit titles starting with Release
regex=^Release(.*)
ignore=title-max-length,body-min-length
# ignore all rules by setting ignore to 'all'
# ignore=all

[ignore-by-body]
# Match commits message bodies that have a line that contains 'release'
regex=(.*)release(.*)
ignore=all

If you just want to ignore certain lines in a commit, you can do that using the ignore-body-lines rule.

# Ignore all lines that start with 'Co-Authored-By'
[ignore-body-lines]
regex=^Co-Authored-By

Warning

When ignoring specific lines, gitlint will no longer be aware of them while applying other rules. This can sometimes be confusing for end-users, especially as line numbers of violations will typically no longer match line numbers in the original commit message. Make sure to educate your users accordingly.

Note

If you want to implement more complex ignore rules according to your own logic, you can do so using user-defined configuration rules.

Named Rules

Introduced in gitlint v0.14.0

Named rules allow you to have multiple of the same rules active at the same time, which allows you to enforce the same rule multiple times but with different options. Named rules are so-called because they require an additional unique identifier (i.e. the rule name) during configuration.

Warning

Named rules is an advanced topic. It's easy to make mistakes by defining conflicting instances of the same rule. For example, by defining 2 body-max-line-length rules with different line-length options, you obviously create a conflicting situation. Gitlint does not do any resolution of such conflicts, it's up to you to make sure any configuration is non-conflicting. So caution advised!

Defining a named rule is easy, for example using your .gitlint file:

# By adding the following section, you will add a second instance of the
# title-must-not-contain-word (T5) rule (in addition to the one that is enabled
# by default) with the name 'extra-words'.
[title-must-not-contain-word:extra-words]
words=foo,bar

# So the generic form is
# [<rule-id-or-name>:<your-chosen-name>]
# Another example, referencing the rule type by id
[T5:more-words]
words=hur,dur

# You can add as many additional rules and you can name them whatever you want
# The only requirement is that names cannot contain whitespace or colons (:)
[title-must-not-contain-word:This-Can_Be*Whatever$YouWant]
words=wonderwoman,batman,power ranger

When executing gitlint, you will see the violations from the default title-must-not-contain-word (T5) rule, as well as the violations caused by the additional Named Rules.

$ gitlint 
1: T5 Title contains the word 'WIP' (case-insensitive): "WIP: foo wonderwoman hur bar"
1: T5:This-Can_Be*Whatever$YouWant Title contains the word 'wonderwoman' (case-insensitive): "WIP: foo wonderwoman hur bar"
1: T5:extra-words Title contains the word 'foo' (case-insensitive): "WIP: foo wonderwoman hur bar"
1: T5:extra-words Title contains the word 'bar' (case-insensitive): "WIP: foo wonderwoman hur bar"
1: T5:more-words Title contains the word 'hur' (case-insensitive): "WIP: foo wonderwoman hur bar"

Named rules are further treated identical to all other rules in gitlint:

  • You can reference them by their full name, when e.g. adding them to your ignore configuration
# .gitlint file example
[general]
ignore=T5:more-words,title-must-not-contain-word:extra-words

Exit codes

Gitlint uses the exit code as a simple way to indicate the number of violations found. Some exit codes are used to indicate special errors as indicated in the table below.

Because of these special error codes and the fact that bash only supports exit codes between 0 and 255, the maximum number of violations counted by the exit code is 252. Note that gitlint does not have a limit on the number of violations it can detect, it will just always return with exit code 252 when the number of violations is greater than or equal to 252.

Exit Code Description
253 Wrong invocation of the gitlint command.
254 Something went wrong when invoking git.
255 Invalid gitlint configuration