Determine previous tag

RELEASE.md

@@ -6,5 +6,5 @@ https://github.com/kubernetes-sigs/controller-runtime/blob/main/RELEASE.md
 1. Create a new release branch from main: `git checkout -b release-<MAJOR.MINOR>`
 2. Push the new branch to the remote repository: ` git push --set-upstream origin release-<MAJOR.MINOR>`
 3. Fetch all tags from the remote: `git fetch --all --tags`
-4. Generate the release notes from the previous tag: `go run ./hack/notes --from vMAJOR.MINOR.PATCH`
+4. Generate the release notes: `go run ./hack/notes`
 5. Create a new release in GitHub from the release branch, pasting the generated release notes

hack/notes/notes.go

@@ -42,12 +42,16 @@ func main() {
 }
 
 func run(from, to string) error {
-	if from == "" {
-		return fmt.Errorf("Git reference to start from must be specified")
-	}
 	if to == "" {
 		to = "HEAD"
 	}
+	var err error
+	if from == "" {
+		from, err = previousTag(to)
+		if err != nil {
+			return err
+		}
+	}
 
 	cmd := exec.Command("git", "rev-list", fmt.Sprintf("%s..%s", from, to), "--pretty=format:%B")
 	out, err := cmd.CombinedOutput()
@@ -106,3 +110,12 @@ func run(from, to string) error {
 
 	return nil
 }
+
+func previousTag(to string) (string, error) {
+	cmd := exec.Command("git", "describe", "--abbrev=0", "--tags", fmt.Sprintf("%s^", to))
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(string(out)), nil
+}