Every git branch and commit contains a Jira ID string, even down to "description" fields in resource properties or meta tags.
The idea is a future engineer who I will never meet has a starting point to understand the context of the change.
Projects on GitLab get a "release" too which contains the Jira ID, or possibly multiple in the auto-generated CHANGELOG.
It's not perfect and does require good discipline however I feel a professional responsibility to make the extra effort.