Commit Lint for Danger

This is a Danger Plugin that ensures nice and tidy commit messages. The checks performed on each commit message are inspired by Tim Pope's blog post on good commit messages, echoed by git's own documentation on the subject.

$ gem install danger-commit_lint

Simply add this to your Dangerfile:

commit_lint.check

That will check each commit in the PR to ensure the following is true:

• Commit subject begins with a capital letter (subject_cap)
• Commit subject is more than one word (subject_words)
• Commit subject is no longer than 50 characters (subject_length)
• Commit subject does not end in a period (subject_period)
• Commit subject and body are separated by an empty line (empty_line)

By default, Commit Lint fails, but you can configure this behavior.

Configuring Commit Lint is done by passing a hash. The four keys that can be passed are:

• disable
• fail
• warn
• limit

The first three of these keys can accept either the symbol :all or an array of checks. Here are some ways you could configure Commit Lint:

# warn on all checks (instead of failing)
commit_lint.check warn: :all

# disable the `subject_period` check
commit_lint.check disable: [:subject_period]

Remember, by default all checks are run and they will fail. Think of this as the default:

commit_lint.check fail: :all

Also note that there is one more way that Commit Lint can behave:

commit_lint.check disable: :all

This will actually throw a warning that Commit Lint isn't doing anything.

The limit key allows you to limit checks to the first n commits (oldest to newest). This can be useful for PR workflows when squashing before merge where you want the initial commit message to be linted, but want to exclude additional commits pushed in response to change requests during a code review.

# limit checks to only the first (oldest) commit
commit_lint.check limit: 1