rhcos: handle new RHEL-based version strings

As part of openshift/enhancements#1637, the
version string for RHCOS will change from being OCP+RHEL-based (e.g.
419.96...) to being purely RHEL-based (e.g. 9.6...).

Adapt the logic for this new scheme so that it links to the right
stream.

We should eventually clean this up though so that the stream name is
available more directly to the release controller so that it doesn't
need to do any guessing.

pkg/rhcos/rhcos.go

@@ -31,7 +31,11 @@ var (
 	reMdCentOSCoSDiff    = regexp.MustCompile(`\* CentOS Stream CoreOS upgraded from ((\d)(\d+)\.[\w\.\-]+) to ((\d)(\d+)\.[\w\.\-]+)\n`)
 	reMdCentOSCoSVersion = regexp.MustCompile(`\* CentOS Stream CoreOS ((\d)(\d+)\.[\w\.\-]+)\n`)
 
-	reCoreOsVersion = regexp.MustCompile(`((\d)(\d+))\.(\d+)\.(\d+)-(\d+)`)
+	// regex for RHCOS in < 4.19, where the version string was e.g. 418.94.202410090804-0
+	reOcpCoreOsVersion = regexp.MustCompile(`((\d)(\d+))\.(\d+)\.(\d+)-(\d+)`)
+
+	// regex for RHCOS in >= 4.19, where the version string was e.g. 9.6.20250121-0
+	reRhelCoreOsVersion = regexp.MustCompile(`(\d+)\.(\d+)\.(\d+)-(\d+)`)
 )
 
 func TransformMarkDownOutput(markdown, fromTag, toTag, architecture, architectureExtension string) (string, error) {
@@ -139,31 +143,37 @@ func TransformJsonOutput(output, architecture, architectureExtension string) (st
 }
 
 func getRHCoSReleaseStream(version, architectureExtension string) (string, bool) {
-	if m := reCoreOsVersion.FindStringSubmatch(version); m != nil {
-		ts, err := strconv.Atoi(m[5])
-		if err != nil {
-			return "", false
-		}
-		minor, err := strconv.Atoi(m[3])
-		if err != nil {
-			return "", false
-		}
-		switch {
-		case ts > changeoverTimestamp && minor >= 9:
-
-			// TODO: This should hopefully only be temporary...
-			versionMap := map[string]string{
-				"92": "9.2",
-				"94": "9.4",
-				"96": "9.6",
+	if strings.HasPrefix(version, "4") {
+		if m := reOcpCoreOsVersion.FindStringSubmatch(version); m != nil {
+			ts, err := strconv.Atoi(m[5])
+			if err != nil {
+				return "", false
 			}
-			if version, ok := versionMap[m[4]]; ok {
-				return fmt.Sprintf("prod/streams/%s.%s-%s", m[2], m[3], version), true
+			minor, err := strconv.Atoi(m[3])
+			if err != nil {
+				return "", false
 			}
+			switch {
+			case ts > changeoverTimestamp && minor >= 9:
 
-			return fmt.Sprintf("prod/streams/%s.%s", m[2], m[3]), true
-		default:
-			return fmt.Sprintf("releases/rhcos-%s.%s%s", m[2], m[3], architectureExtension), true
+				// TODO: This should hopefully only be temporary...
+				versionMap := map[string]string{
+					"92": "9.2",
+					"94": "9.4",
+					"96": "9.6",
+				}
+				if version, ok := versionMap[m[4]]; ok {
+					return fmt.Sprintf("prod/streams/%s.%s-%s", m[2], m[3], version), true
+				}
+
+				return fmt.Sprintf("prod/streams/%s.%s", m[2], m[3]), true
+			default:
+				return fmt.Sprintf("releases/rhcos-%s.%s%s", m[2], m[3], architectureExtension), true
+			}
+		}
+	} else {
+		if m := reRhelCoreOsVersion.FindStringSubmatch(version); m != nil {
+			return fmt.Sprintf("prod/streams/rhel-%s.%s", m[1], m[2]), true
 		}
 	}
 	return "", false