index.html.haml

---
title: Keep a Changelog
description: Don’t let your friends dump git logs into changelogs.
language: en
version: 1.1.0
---
.header
  .title
    %h1= current_page.data.title
    %h2= current_page.data.description

  = link_to data.links.changelog do
    Version
    %strong= current_page.metadata[:page][:version]

  %pre.changelog{ lang: "en" }= File.read("CHANGELOG.md")

.answers
  %h3#what
    %a.anchor{ href: "#what", aria_hidden: "true" }
    What is a changelog?

  %p
    A changelog is a file which contains a curated, chronologically
    ordered list of notable changes for each version of a project.

  %h3#why
    %a.anchor{ href: "#why", aria_hidden: "true" }
    Why keep a changelog?

  %p
    To make it easier for users and contributors to see precisely what
    notable changes have been made between each release (or version) of
    the project.

  %h3#who
    %a.anchor{ href: "#who", aria_hidden: "true" }
    Who needs a changelog?

  %p
    People do. Whether consumers or developers, the end users of
    software are human beings who care about what's in the software. When
    the software changes, people want to know why and how.

.good-practices
  %h3#how
    %a.anchor{ href: "#how", aria_hidden: "true" }
    How do I make a good changelog?

  %h4#principles
    %a.anchor{ href: "#principles", aria_hidden: "true" }
    Guiding Principles

  %ul
    %li
      Changelogs are <em>for humans</em>, not machines.
    %li
      There should be an entry for every single version.
    %li
      The same types of changes should be grouped.
    %li
      Versions and sections should be linkable.
    %li
      The latest version comes first.
    %li
      The release date of each version is displayed.
    %li
      Mention whether you follow #{link_to "Semantic Versioning", data.links.semver}.

  %a.anchor{ href: "#types", aria_hidden: "true" }
  %h4#types Types of changes

  %p
    Each type of change below is a section heading under a version. List sections in
    the following order of urgency (omit empty sections):

  %ul
    %li
      %code Security
      for fixes to known security vulnerabilities and advisories.
    %li
      %code Removed
      for now removed features.
    %li
      %code Changed
      for changes in existing functionality; prefix breaking changes so they stand out
      (e.g.
      %code BREAKING:
      or
      %strong BREAKING:
      ).
    %li
      %code Deprecated
      for soon-to-be removed features.
    %li
      %code Fixed
      for any bug fixes unrelated to security.
    %li
      %code Added
      for new features.

.effort

  %h3#effort
    %a.anchor{ href: "#effort", aria_hidden: "true" }
    How can I reduce the effort required to maintain a changelog?

  %p
    Keep an <code>Unreleased</code> section at the top to track upcoming
    changes.

  %p This serves two purposes:

  %ul
    %li
      People can see what changes they might expect in upcoming releases
    %li
      At release time, you can move the <code>Unreleased</code> section
      changes into a new release version section.

.bad-practices
  %h3#bad-practices
    %a.anchor{ href: "#bad-practices", aria_hidden: "true" }
    Can changelogs be bad?

  %p Yes. Here are a few ways they can be less than useful.

  %h4#log-diffs
    %a.anchor{ href: "#log-diffs", aria_hidden: "true" }
    Commit log diffs

  %p
    Using commit log diffs as changelogs is a bad idea: they're full of
    noise. Things like merge commits, commits with obscure titles,
    documentation changes, etc.

  %p
    The purpose of a commit is to document a step in the evolution of
    the source code. Some projects clean up commits, some don't.

  %p
    The purpose of a changelog entry is to document the noteworthy
    difference, often across multiple commits, to communicate them
    clearly to end users.

  %h4#ignoring-deprecations
    %a.anchor{ href: "#ignoring-deprecations", aria_hidden: "true" }
    Ignoring Deprecations

  %p
    When people upgrade from one version to another, it should be
    painfully clear when something will break. It should be possible to
    upgrade to a version that lists deprecations, remove what's
    deprecated, then upgrade to the version where the deprecations
    become removals.

  %p
    That said, if you do nothing else, list removals and breaking changes
    in your changelog.

  %h4#confusing-dates
    %a.anchor{ href: "#confusing-dates", aria_hidden: "true" }
    Confusing Dates

  %p
    Regional date formats vary throughout the world and it's often
    difficult to find a human-friendly date format that feels intuitive
    to everyone. The advantage of dates formatted like
    <code>2017-07-17</code> is that they follow the order of largest to
    smallest units: year, month, and day. This format also doesn't
    overlap in ambiguous ways with other date formats, unlike some
    regional formats that switch the position of month and day numbers.
    These reasons, and the fact this date format is an
    #{link_to "ISO standard", data.links.isodate}, are why it is the recommended date
    format for changelog entries.

  %h4#inconsistent-changes
    %a.anchor{ href: "#inconsistent-changes", aria_hidden: "true" }
    Inconsistent Changes

  %p
    A changelog which only mentions some of the changes can be as dangerous
    as not having a changelog. While many of the changes may not be
    relevant - for instance, removing a single whitespace may not need
    to be recorded in all instances - any important changes should be
    mentioned in the changelog. By inconsistently applying changes,
    your users may mistakenly think that the changelog is the single source
    of truth. It ought to be. With great power comes great responsibility -
    having a good changelog means having a consistently updated changelog.

  %aside
    There’s more. Help me collect these antipatterns by
    = link_to "opening an issue", data.links.issue
    or a pull request.

.frequently-asked-questions
  %h3#frequently-asked-questions
    %a.anchor{ href: "#frequently-asked-questions", aria_hidden: "true" }
    Frequently Asked Questions

  %h4#standard
    %a.anchor{ href: "#standard", aria_hidden: "true" }
    Is there a standard changelog format?

  %p
    Not really. There's the #{link_to "GNU changelog style guide", data.links.gnustyle},
    or the #{link_to "two-paragraph-long GNU NEWS file", data.links.gnunews}
    "guideline". Both are inadequate or insufficient.

  %p
    This project aims to be
    = link_to "a better changelog convention.", data.links.changelog
    It comes from observing good practices in the open source
    community and gathering them.

  %p
    Healthy criticism, discussion and suggestions for improvements
    = link_to "are welcome.", data.links.issue


  %h4#filename
    %a.anchor{ href: "#filename", aria_hidden: "true" }
    What should the changelog file be named?

  %p
    Call it <code>CHANGELOG.md</code>. Some projects use
    <code>HISTORY</code>, <code>NEWS</code> or <code>RELEASES</code>.

  %p
    While it's easy to think that the name of your changelog file
    doesn't matter that much, why make it harder for your end users to
    consistently find notable changes?

  %h4#github-releases
    %a.anchor{ href: "#github-releases", aria_hidden: "true" }
    What about GitHub Releases?

  %p
    It's a great initiative. #{link_to "Releases", data.links.github_releases} can be used to
    turn simple git tags (for example a tag named <code>v1.0.0</code>)
    into rich release notes by manually adding release notes or it can
    pull annotated git tag messages and turn them into notes.

  %p
    GitHub Releases create a non-portable changelog that can only be
    displayed to users within the context of GitHub. It's possible to
    make them look very much like the Keep a Changelog format, but it
    tends to be a bit more involved.

  %p
    The current version of GitHub releases is also arguably not very
    discoverable by end-users, unlike the typical uppercase files
    (<code>README</code>, <code>CONTRIBUTING</code>, etc.). Another
    minor issue is that the interface doesn't currently offer links to
    commit logs between each release.

  %h4#automatic
    %a.anchor{ href: "#automatic", aria_hidden: "true" }
    Can changelogs be automatically parsed?

  %p
    It’s difficult, because people follow wildly different formats and
    file names.

  %p
    #{link_to "Vandamme", data.links.vandamme} is a Ruby gem created by the
    Gemnasium team and which parses many (but
    not all) open source project changelogs.


  %h4#yanked
    %a.anchor{ href: "#yanked", aria_hidden: "true" }
    What about yanked releases?

  %p
    Yanked releases are versions that had to be pulled because of a
    serious bug or security issue. Often these versions don't even
    appear in change logs. They should. This is how you should display
    them:

  %p <code>## [0.0.5] - 2014-12-13 [YANKED]</code>

  %p
    The <code>[YANKED]</code> tag is loud for a reason. It's important
    for people to notice it. Since it's surrounded by brackets it's also
    easier to parse programmatically.


  %h4#rewrite
    %a.anchor{ href: "#rewrite", aria_hidden: "true" }
    Should you ever rewrite a changelog?

  %p
    Sure. There are always good reasons to improve a changelog. I
    regularly open pull requests to add missing releases to open source
    projects with unmaintained changelogs.

  %p
    It's also possible you may discover that you forgot to address a
    breaking change in the notes for a version. It's obviously important
    for you to update your changelog in this case.


  %h4#contribute
    %a.anchor{ href: "#contribute", aria_hidden: "true" }
    How can I contribute?

  %p
    This document is not the <strong>truth</strong>; it’s my carefully
    considered opinion, along with information and examples I gathered.

  %p
    This is because I want our community to reach a consensus. I believe
    the discussion is as important as the end result.

  %p
    So please <strong>#{link_to "pitch in", data.links.repo}</strong>.

.press
  %h3 Conversations
  %p
    I went on #{link_to "The Changelog podcast", data.links.thechangelog}
    to talk about why maintainers and contributors should care about changelogs,
    and also about the motivations behind this project.