Add default GitHub API client (golang-migrate#501)

source/github/README.md

@@ -2,12 +2,14 @@
 
 This driver is catered for those that want to source migrations from [github.com](https://github.com). The URL scheme doesn't require a hostname, as it just simply defaults to `github.com`.
 
-`github://user:personal-access-token@owner/repo/path#ref`
+Authenticated client: `github://user:personal-access-token@owner/repo/path#ref`
+
+Unauthenticated client: `github://owner/repo/path#ref`
 
 | URL Query  | WithInstance Config | Description |
 |------------|---------------------|-------------|
-| user | | The username of the user connecting |
-| personal-access-token | | An access token from GitHub (https://github.com/settings/tokens) |
+| user | | (optional) The username of the user connecting |
+| personal-access-token | | (optional) An access token from GitHub (https://github.com/settings/tokens) |
 | owner | | the repo owner |
 | repo | | the name of the repository |
 | path | | path in repo to migrations |

source/github/github.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"net/http"
 	nurl "net/url"
 	"os"
 	"path"
@@ -48,22 +49,23 @@ func (g *Github) Open(url string) (source.Driver, error) {
 		return nil, err
 	}
 
-	if u.User == nil {
-		return nil, ErrNoUserInfo
-	}
-
-	password, ok := u.User.Password()
-	if !ok {
-		return nil, ErrNoUserInfo
-	}
+	// client defaults to http.DefaultClient
+	var client *http.Client
+	if u.User != nil {
+		password, ok := u.User.Password()
+		if !ok {
+			return nil, ErrNoUserInfo
+		}
 
-	tr := &github.BasicAuthTransport{
-		Username: u.User.Username(),
-		Password: password,
+		tr := &github.BasicAuthTransport{
+			Username: u.User.Username(),
+			Password: password,
+		}
+		client = tr.Client()
 	}
 
 	gn := &Github{
-		client:     github.NewClient(tr.Client()),
+		client:     github.NewClient(client),
 		migrations: source.NewMigrations(),
 		options:    &github.RepositoryContentGetOptions{Ref: u.Fragment},
 	}
@@ -144,7 +146,7 @@ func (g *Github) Close() error {
 	return nil
 }
 
-func (g *Github) First() (version uint, er error) {
+func (g *Github) First() (version uint, err error) {
 	g.ensureFields()
 
 	if v, ok := g.migrations.First(); !ok {

source/github/github_test.go

@@ -2,10 +2,12 @@ package github
 
 import (
 	"bytes"
+	"fmt"
 	"io/ioutil"
 	"testing"
 
 	st "github.com/golang-migrate/migrate/v4/source/testing"
+	"github.com/stretchr/testify/assert"
 )
 
 var GithubTestSecret = "" // username:token
@@ -30,3 +32,28 @@ func Test(t *testing.T) {
 
 	st.Test(t, d)
 }
+
+func TestDefaultClient(t *testing.T) {
+	g := &Github{}
+	owner := "golang-migrate"
+	repo := "migrate"
+	path := "source/github/examples/migrations"
+
+	url := fmt.Sprintf("github://%s/%s/%s", owner, repo, path)
+	d, err := g.Open(url)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ver, err := d.First()
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, uint(1085649617), ver)
+
+	ver, err = d.Next(ver)
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, uint(1185749658), ver)
+}