Add deprecated HTTPFallback for package compatibility

Signed-off-by: Derek McGowan <derek@mcg.dev>

remotes/docker/resolver.go

@@ -763,3 +763,37 @@ func isTLSError(err error) bool {
 
 	return false
 }
+
+// HTTPFallback is an http.RoundTripper which allows fallback from https to http
+// for registry endpoints with configurations for both http and TLS, such as
+// defaulted localhost endpoints.
+//
+// Deprecated: Use NewHTTPFallback instead.
+type HTTPFallback struct {
+	http.RoundTripper
+}
+
+func (f HTTPFallback) RoundTrip(r *http.Request) (*http.Response, error) {
+	resp, err := f.RoundTripper.RoundTrip(r)
+	var tlsErr tls.RecordHeaderError
+	if errors.As(err, &tlsErr) && string(tlsErr.RecordHeader[:]) == "HTTP/" {
+		// server gave HTTP response to HTTPS client
+		plainHTTPUrl := *r.URL
+		plainHTTPUrl.Scheme = "http"
+
+		plainHTTPRequest := *r
+		plainHTTPRequest.URL = &plainHTTPUrl
+
+		if r.Body != nil && r.GetBody != nil {
+			body, err := r.GetBody()
+			if err != nil {
+				return nil, err
+			}
+			plainHTTPRequest.Body = body
+		}
+
+		return f.RoundTripper.RoundTrip(&plainHTTPRequest)
+	}
+
+	return resp, err
+}