JIRA-123 Concise description of the change
JIRA-123 Componentname: concise description of the change
Nice and simple... commit against a ticket number and write long form information there as required. Linking code changes to general systems is often required for compliance/change control reasons anyway.
In component-based repos, I might add a prefix specifying the feature being worked on. But more often than not I'll be including that in the description anyway.
I'm not a fan of essays in commit messages - if the information is critical to understanding the code it should be in a comment. If the information is relevant to non-devs, it needs to be exposed somewhere else.