upload/koji: allow passing a custom transport to koji.Login

In the near future, we will need to communicate with Koji using HTTPS.
This will surely bring the need for ignoring bad certificates/providing
our own self-signed ones. Thus, this commit prepares the Koji integration
by adding a way to accept a custom http transport which can be used to
customize the TLS settings.

internal/upload/koji/koji.go

@@ -106,9 +106,11 @@ type CGImportResult struct {
 	BuildID int `xmlrpc:"build_id"`
 }
 
-func Login(server, user, password string) (*Koji, error) {
-	// Create a temporary xmlrpc client with the default http transport
-	// as we don't need sessionID, key nor callnum yet.
+func Login(server, user, password string, transport http.RoundTripper) (*Koji, error) {
+	// Create a temporary xmlrpc client.
+	// The API doesn't require sessionID, sessionKey and callnum yet,
+	// so there's no need to use the custom Koji RoundTripper,
+	// let's just use the one that the called passed in.
 	loginClient, err := xmlrpc.NewClient(server, http.DefaultTransport)
 	if err != nil {
 		return nil, err
@@ -130,6 +132,7 @@ func Login(server, user, password string) (*Koji, error) {
 		sessionID:  reply.SessionID,
 		sessionKey: reply.SessionKey,
 		callnum:    0,
+		transport:  transport,
 	}
 
 	client, err := xmlrpc.NewClient(server, kojiTransport)
@@ -277,6 +280,7 @@ type Transport struct {
 	sessionID  int64
 	sessionKey string
 	callnum    int
+	transport  http.RoundTripper
 }
 
 // RoundTrip implements the RoundTripper interface, using the default
@@ -303,5 +307,5 @@ func (rt *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
 	// Each call is given a unique callnum.
 	rt.callnum++
 
-	return http.DefaultTransport.RoundTrip(rClone)
+	return rt.transport.RoundTrip(rClone)
 }

internal/upload/koji/koji_test.go

@@ -6,6 +6,7 @@ import (
 	"crypto/rand"
 	"io"
 	"io/ioutil"
+	"net/http"
 	"os"
 	"os/exec"
 	"strconv"
@@ -31,7 +32,7 @@ func TestKojiImport(t *testing.T) {
 	// koji needs to specify a directory to which the upload should happen, let's reuse the build name
 	uploadDirectory := buildName
 
-	k, err := koji.Login(server, user, password)
+	k, err := koji.Login(server, user, password, http.DefaultTransport)
 	require.NoError(t, err)
 
 	defer func() {