3. Commit Style

When writing commit messages, please think carefully about the purpose and scope of the change you are making: describe briefly what the change does, and describe in detail why it does it. This helps to ensure that changes to the code-base are transparent and approachable to reviewers, and it allows us to keep a more accurate changelog. You may use Markdown in commit messages.

A good commit message provides all the background information needed for reviewers to understand the intent and rationale of the patch. This information is also useful for future reference. For example:

  • What does the patch do?

  • What motivated it?

  • What impact does it have?

  • How was it tested?

  • Have alternatives been considered? Why did you choose this approach over another one?

  • If it fixes an issue, include a reference.

    • Github prescribes a format for issue fixes that can be used within the commit message:

      Fixes TF-RMM/tf-rmm#<issue-number>

Commit messages are expected to be of the following form, based on conventional commits:

<type>[optional scope]: <description>

[optional body]

[optional trailer(s)]

The following types are permissible :




A new feature


A bug fix


Changes that affect the build system or external dependencies


Documentation-only changes


A code change that improves performance


A code change that neither fixes a bug nor adds a feature


Changes that revert a previous change


Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc.)


Adding missing tests or correcting existing tests


Any other change

The permissible scopes are more flexible, and we recommend that they match the directory where the patch applies (or where the main subject of the patch is, in case of changes accross several directories).

The following example commit message demonstrates the use of the refactor type and the lib/arch scope:

refactor(lib/arch): ...

This change introduces ....

Change-Id: ...
Signed-off-by: ...

In addition, the width of the commit message must be no more than 72 characters.

3.1. Mandated Trailers

Commits are expected to be signed off with the Signed-off-by: trailer using your real name and email address. You can do this automatically by committing with Git’s -s flag.

There may be multiple Signed-off-by: lines depending on the history of the patch. See License and Copyright for Contributions for guidance on this.

Ensure that each commit also has a unique Change-Id: line. If you have cloned the repository using the “Clone with commit-msg hook” clone method, then this should be done automatically for you.

More details may be found in the Gerrit Change-Ids documentation.