Commit message from a diff

---name: commit-messagedescription: "Write a commit message from a diff: a subject line that states what was found, then prose explaining why the change was made."metadata:  title: "Commit message from a diff"  category: engineering  tags: [git, writing]--- ## When to use this A change is ready and needs a message. Also when rewriting one that says onlywhat the diff already says. ## How 1. Read the whole diff before writing anything. A message written from the   branch name describes an intention, not a change.2. Make the subject the finding rather than the activity: "the tray icon was a   black square, not a missing file" beats "fix tray icon". Under 72 characters,   no trailing full stop.3. Then the body, in prose and in paragraphs, answering WHY -- the diff already   answers what. Name the cause you found, the symptom somebody saw, and the   fix you considered and rejected.4. Attach every claim to something checkable: a file and line, a quoted error, a   measured number. "This is faster" is an opinion. "2.1s to 0.3s" is a finding.5. Say what the change does not fix, when it leaves something standing. Leave out a walk through the hunks and a list of the files touched. A readergets both from git show, and a body that can be deleted without losing anargument was a restatement of the diff.