HACK: Have private/public fields for the webhook URL

We can't just use a public field because the caller may clobber it. If they
do clobber it, we've then lost the ability to set it back to what it was because
we don't store another copy anywhere. This patch fixes it by keeping a private
ref and always clobbering on Register().

This is horrible. We need to separate internal-storage and external-fields
better.

src/github.com/matrix-org/go-neb/services/travisci/travisci.go

@@ -50,8 +50,9 @@ var httpClient = &http.Client{}
 //   }
 type Service struct {
 	types.DefaultService
+	webhookEndpointURL string
 	// The URL which should be added to .travis.yml - Populated by Go-NEB after Service registration.
-	WebhookEndpointURL string `json:"webhook_url"`
+	WebhookURL string `json:"webhook_url"`
 	// A map from Matrix room ID to Github-style owner/repo repositories.
 	Rooms map[string]struct {
 		// A map of "owner/repo" to configuration information
@@ -237,6 +238,7 @@ func (s *Service) OnReceiveWebhook(w http.ResponseWriter, req *http.Request, cli
 
 // Register makes sure the Config information supplied is valid.
 func (s *Service) Register(oldService types.Service, client *matrix.Client) error {
+	s.WebhookURL = s.webhookEndpointURL
 	for _, roomData := range s.Rooms {
 		for repo := range roomData.Repos {
 			match := ownerRepoRegex.FindStringSubmatch(repo)
@@ -283,7 +285,7 @@ func init() {
 	types.RegisterService(func(serviceID, serviceUserID, webhookEndpointURL string) types.Service {
 		return &Service{
 			DefaultService:     types.NewDefaultService(serviceID, serviceUserID, ServiceType),
-			WebhookEndpointURL: webhookEndpointURL,
+			webhookEndpointURL: webhookEndpointURL,
 		}
 	})
 }