For great commit messages, just browse the git history of the Linux kernel where this is the standard. The first line always mentions the subsystem affected by

For great commit messages, just browse the git history of the Linux kernel where this is the standard. The first line always mentions the subsystem affected by the change, followed by a one-line imperative-mood summary of the change. Subsequently, three questions are answered in as much detail as possible: 1. What is the current behaviour? 2. What led to this change? 3. What is the new behaviour after applying this change? Example: "Currently, code does X. When running test case T, unexpected behaviour U was observed. This is because of reason R. Fix this by doing F."