• Add a trailer to a Git commit
• Create a changelog
  • From the API
  • From the GitLab CLI
• Customize the changelog output
  • Custom templates
  • Template data
  • Customize the tag format when extracting versions
• Reverted commit handling
• Related topics

Changelogs

Changelogs are generated based on commit titles and Git trailers. To be included in a changelog, a commit must contain a specific Git trailer. Changelogs are generated from commit titles, and categorized by Git trailer type. You can enrich changelog entries with additional data, such as a link to the merge request or details about the commit author. Changelog formats can be customized with a template.

Each section in the default changelog has a title containing the version number and release date, like this:

## 1.0.0 (2021-01-05)

### Features (4 changes)

- [Feature 1](gitlab-org/gitlab@123abc) by @alice ([merge request](gitlab-org/gitlab!123))
- [Feature 2](gitlab-org/gitlab@456abc) ([merge request](gitlab-org/gitlab!456))
- [Feature 3](gitlab-org/gitlab@234abc) by @steve
- [Feature 4](gitlab-org/gitlab@456)

The date format for sections can be customized, but the rest of the title cannot. When adding new sections, GitLab parses these titles to determine where to place the new information in the file. GitLab sorts sections according to their versions, not their dates.

Each section contains changes sorted by category (like Features), and the format of these sections can be changed. The section names derive from the values of the Git trailer used to include or exclude commits.

Commits for changelogs can be retrieved when operating on a mirror. GitLab itself uses this feature, because patch releases can include changes from both public projects and private security mirrors.

Add a trailer to a Git commit

You can add trailers manually when you write a commit message. To include a commit using the default trailer of Changelog and categorize it as a feature, add the string Changelog: feature to your commit message, like this:

<Commit message subject>

<Commit message description>

Changelog: feature

Create a changelog

Changelogs are generated from the command line, using either the API or the GitLab CLI. The changelog output is formatted in Markdown, and you can customize it.

From the API

To use the API to generate changelogs with a curl command, see Add changelog data to a changelog file in the API documentation.

From the GitLab CLI

• Introduced in glab version 1.30.0.

Prerequisites:

• You have installed and configured the GitLab CLI, version 1.30.0 or later.
• Your repository’s tag naming schema matches the expected tag naming format.
• Commits include changelog trailers.

To generate the changelog:

1. Update your local copy of your repository with git fetch.
2. To generate a changelog for the current version (as determined by git describe --tags) with the default options:
   • Run the command glab changelog generate.
   • To save the output to a file, run the command glab changelog generate > <filename>.md.

3. To generate a changelog with customized options, run the command glab changelog generate and append your desired options. Some options include:

   • --config-file [string]: The path to the changelog configuration file in your project’s Git repository. This file must exist in your project’s Git repository. Defaults to .gitlab/changelog_config.yml.
   • Commit range:
     • --from [string]: The start of the range of commits (as a SHA) to use for generating the changelog. This commit itself isn’t included in the changelog.
     • --to [string]: The end of the range of commits (as a SHA) to use for generating the changelog. This commit is included in the list. Defaults to the HEAD of the default project branch.
   • --date [string]: The date and time of the release, in ISO 8601 (2016-03-11T03:45:40Z) format. Defaults to the current time.
   • --trailer [string]: The Git trailer to use for including commits. Defaults to Changelog.
   • --version [string]: The version to generate the changelog for.

To learn more about the parameters available in GitLab CLI, run glab changelog generate --help. See the API documentation for definitions and usage.

Customize the changelog output

To customize the changelog output, edit the changelog configuration file, and commit these changes to your project’s Git repository. The default location for this configuration is .gitlab/changelog_config.yml. The file supports these variables:

• date_format: The date format, in strftime format, used in the title of the newly added changelog data.
• template: A custom template to use when generating the changelog data.
• include_groups: A list of group full paths containing users whose contributions should be credited regardless of project membership. The user generating the changelog must have access to each group for credit to be given.

• categories: A hash that maps raw category names to the names to use in the changelog. To alter the names displayed in the changelog, add these lines to your configuration file and edit them to meet your needs. This example renders the category titles as ### Features, ### Bug fixes, and ### Performance improvements:

  ---
  categories:
    feature: Features
    bug: Bug fixes
    performance: Performance improvements
  

Custom templates

Category sections are generated using a template. The default template:

{% if categories %}
{% each categories %}
### {{ title }} ({% if single_change %}1 change{% else %}{{ count }} changes{% end %})

{% each entries %}
- [{{ title }}]({{ commit.web_url }})\
{% if author.credit %} by {{ author.reference }}{% end %}\
{% if merge_request %} ([merge request]({{ merge_request.web_url }})){% end %}

{% end %}

{% end %}
{% else %}
No changes.
{% end %}

The {% ... %} tags are for statements, and {{ ... }} is used for printing data. Statements must be terminated using a {% end %} tag. Both the if and each statements require a single argument.

For example, for a variable called valid, you can display “yes” when this value is true, and display “nope” otherwise by doing the following:

{% if valid %}
yes
{% else %}
nope
{% end %}

The use of else is optional. A value is considered true when it’s a non-empty value or boolean true. Empty arrays and hashes are considered false.

Looping is done using each, and variables inside a loop are scoped to it. Referring to the current value in a loop is done using the variable tag {{ it }}. Other variables read their value from the current loop value. Take this template for example:

{% each users %}
{{name}}
{% end %}

Assuming users is an array of objects, each with a name field, this would then print the name of every user.

Using variable tags, you can access nested objects. For example, {{ users.0.name }} prints the name of the first user in the users variable.

If a line ends in a backslash, the next newline is ignored. This allows you to wrap code across multiple lines, without introducing unnecessary newlines in the Markdown output.

Tags that use {% and %} (known as expression tags) consume the newline that directly follows them, if any. This means that this:

---
{% if foo %}
bar
{% end %}
---

Compiles into this:

---
bar
---

Instead of this:

---

bar

---

You can specify a custom template in your configuration, like this:

---
template: |
  {% if categories %}
  {% each categories %}
  ### {{ title }}

  {% each entries %}
  - [{{ title }}]({{ commit.web_url }})\
  {% if author.credit %} by {{ author.reference }}{% end %}

  {% end %}

  {% end %}
  {% else %}
  No changes.
  {% end %}

When specifying the template you should use template: | and not template: >, as the latter doesn’t preserve newlines in the template.

Template data

At the top level, the following variable is available:

• categories: an array of objects, one for every changelog category.

In a category, the following variables are available:

• count: the number of entries in this category.
• entries: the entries that belong to this category.
• single_change: a boolean that indicates if there is only one change (true), or multiple changes (false).
• title: the title of the category (after it has been remapped).

In an entry, the following variables are available (here foo.bar means that bar is a sub-field of foo):

• author.contributor: a boolean set to true when the author is not a project member, otherwise false.
• author.credit: a boolean set to true when author.contributor is true or when include_groups is configured, and the author is a member of one of the groups.
• author.reference: a reference to the commit author (for example, @alice).
• commit.reference: a reference to the commit, for example, gitlab-org/gitlab@0a4cdd86ab31748ba6dac0f69a8653f206e5cfc7.
• commit.web_url: a URL to the commit, for example, https://gitlab.com/gitlab-org/gitlab/-/commit/0a4cdd86ab31748ba6dac0f69a8653f206e5cfc7.

• commit.trailers: an object containing all the Git trailers that were present in the commit body.

  These trailers can be referenced using commit.trailers.<name>. For example, assuming the following commit:

  Add some impressive new feature
  
  Changelog: added
  Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/1234
  Status: important
  

  The Changelog, Issue and Status trailers can be accessed in the template as follows:

  {% each entries %}
  {% if commit.trailers.Issue %} ([link to issue]({{ commit.trailers.Issue }})){% end %}
  {% if commit.trailers.Status %}Status: {{ commit.trailers.Status }}{% end %}
  {% end %}
  

• merge_request.reference: a reference to the merge request that first introduced the change (for example, gitlab-org/gitlab!50063).
• merge_request.web_url: a URL to the merge request that first introduced the change (for example, https://gitlab.com/gitlab-org/gitlab/-/merge_requests/50063).
• title: the title of the changelog entry (this is the commit title).

The author and merge_request objects might not be present if the data couldn’t be determined. For example, when a commit is created without a corresponding merge request, no merge request is displayed.

Customize the tag format when extracting versions

GitLab uses a regular expression (using the re2 engine and syntax) to extract a semantic version from tag names. The default regular expression is:

^v?(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<pre>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+(?P<meta>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$

This regular expression is based on the official semantic versioning regular expression, and also includes support for tag names that start with the letter v.

If your project uses a different format for tags, you can specify a different regular expression. The regular expression used must produce the following capture groups. If any of these capture groups are missing, the tag is ignored:

• major
• minor
• patch

The following capture groups are optional:

• pre: If set, the tag is ignored. Ignoring pre tags ensures release candidate tags and other pre-release tags are not considered when determining the range of commits to generate a changelog for.
• meta: Optional. Specifies build metadata.

Using this information, GitLab builds a map of Git tags and their release versions. It then determines what the latest tag is, based on the version extracted from each tag.

To specify a custom regular expression, use the tag_regex setting in your changelog configuration YAML file. For example, this pattern matches tag names such as version-1.2.3 but not version-1.2.

---
tag_regex: '^version-(?P<major>\d+)\.(?P<minor>\d+)\.(?P<patch>\d+)$'

To test if your regular expression is working, you can use websites such as regex101. If the regular expression syntax is invalid, an error is produced when generating a changelog.

Reverted commit handling

To be treated as a revert commit, the commit message must contain the string This reverts commit <SHA>, where SHA is the SHA of the commit to be reverted.

When generating a changelog for a range, GitLab ignores commits both added and reverted in that range. In this example, commit C reverts commit B. Because commit C has no other trailer, only commit A is added to the changelog:

However, if the revert commit (commit C) also contains a changelog trailer, both commits A and C are included in the changelog:

Commit B is skipped.

Related topics

• Changelog-related endpoints in the Repositories API.
• glab changelog in the GitLab CLI documentation.