Optimise basic auth for libgit2 managed transport

The initial implementation was based off upstream, which cause
an initial request to fail, and only then the credentials would
be added into the request.

Signed-off-by: Paulo Gomes <paulo.gomes@weave.works>

Author: Paulo Gomes

pkg/git/libgit2/managed/http.go

@@ -288,12 +288,15 @@ func (self *httpSmartSubtransportStream) sendRequest() error {
 		if err.Error() != git2go.ErrorCodePassthrough.String() {
 			return err
 		}
-	} else {
+	}
+
+	if cred != nil {
+		defer cred.Free()
+
 		userName, password, err = cred.GetUserpassPlaintext()
 		if err != nil {
 			return err
 		}
-		defer cred.Free()
 	}
 
 	for {
@@ -317,23 +320,6 @@ func (self *httpSmartSubtransportStream) sendRequest() error {
 			break
 		}
 
-		if resp.StatusCode == http.StatusUnauthorized {
-			resp.Body.Close()
-
-			cred, err := self.owner.transport.SmartCredentials("", git2go.CredentialTypeUserpassPlaintext)
-			if err != nil {
-				return err
-			}
-			defer cred.Free()
-
-			userName, password, err = cred.GetUserpassPlaintext()
-			if err != nil {
-				return err
-			}
-
-			continue
-		}
-
 		io.Copy(ioutil.Discard, resp.Body)
 		resp.Body.Close()
 		return fmt.Errorf("Unhandled HTTP error %s", resp.Status)