Do not nest transports for Github installation client (#1564)

#1454 modified one of the Github enumeration code paths in a way that broke an integration test by causing one client's transport to be used for the construction of a different client, causing authentication failures. This saves the original transport for use, fixing the test.

pkg/sources/github/github.go

@@ -556,38 +556,41 @@ func (s *Source) enumerateWithApp(ctx context.Context, apiEndpoint string, app *
 		return nil, errors.New(err)
 	}
 
-	// This client is used for most APIs.
-	itr, err := ghinstallation.New(
+	// This client is required to create installation tokens for cloning.
+	// Otherwise, the required JWT is not in the request for the token :/
+	// This client uses the source's original HTTP transport, so make sure
+	// to build it before modifying that transport (such as is done during
+	// the creation of the other API client below).
+	appItr, err := ghinstallation.NewAppsTransport(
 		s.httpClient.Transport,
 		appID,
-		installationID,
 		[]byte(app.PrivateKey))
 	if err != nil {
 		return nil, errors.New(err)
 	}
-	itr.BaseURL = apiEndpoint
+	appItr.BaseURL = apiEndpoint
 
-	s.httpClient.Transport = itr
-	s.apiClient, err = github.NewEnterpriseClient(apiEndpoint, apiEndpoint, s.httpClient)
+	// Does this need to be separate from |s.httpClient|?
+	instHttpClient := common.RetryableHttpClientTimeout(60)
+	instHttpClient.Transport = appItr
+	installationClient, err = github.NewEnterpriseClient(apiEndpoint, apiEndpoint, instHttpClient)
 	if err != nil {
 		return nil, errors.New(err)
 	}
 
-	// This client is required to create installation tokens for cloning.
-	// Otherwise, the required JWT is not in the request for the token :/
-	appItr, err := ghinstallation.NewAppsTransport(
+	// This client is used for most APIs.
+	itr, err := ghinstallation.New(
 		s.httpClient.Transport,
 		appID,
+		installationID,
 		[]byte(app.PrivateKey))
 	if err != nil {
 		return nil, errors.New(err)
 	}
-	appItr.BaseURL = apiEndpoint
+	itr.BaseURL = apiEndpoint
 
-	// Does this need to be separate from |s.httpClient|?
-	instHttpClient := common.RetryableHttpClientTimeout(60)
-	instHttpClient.Transport = appItr
-	installationClient, err = github.NewEnterpriseClient(apiEndpoint, apiEndpoint, instHttpClient)
+	s.httpClient.Transport = itr
+	s.apiClient, err = github.NewEnterpriseClient(apiEndpoint, apiEndpoint, s.httpClient)
 	if err != nil {
 		return nil, errors.New(err)
 	}