REEF commit messages are very stylized. They are valid Markdown and contain:

1. A first line referencing the JIRA and a short summary of what change was done. Focus on the change, not on the bug.
2. A paragraph or more describing the change. Here, focus on the why?, not the what?
3. A formal reference to the JIRA.
4. A formal reference to the pull request.

Example

[REEF-33] Allow Tasks to initiate an Evaluator Heartbeat

  This adds the class HeartBeatTriggerManager which can be used by a Task to
  initiate an Evaluator Heartbeat. It is used by injecting it into the Task.
 
JIRA:
  [REEF-33](https://issues.apache.org/jira/browse/REEF-33)
 
Pull Request:
  Closes #24

As a contributor

• Please make sure the commit message matches the above template.
• Do not add the pull request number, as it will be known only once you file the PR.

As a committer

• Please check the commit message. It is easy to have the URL or such wrong for a JIRA
• Add the pull request number to the commit before merging.