Add PullRequests.GetRaw to download raw content of pull request.

Closes #481.
Updates #6.

github/github.go

@@ -42,6 +42,8 @@ const (
 	mediaTypeV3                = "application/vnd.github.v3+json"
 	defaultMediaType           = "application/octet-stream"
 	mediaTypeV3SHA             = "application/vnd.github.v3.sha"
+	mediaTypeV3Diff            = "application/vnd.github.v3.diff"
+	mediaTypeV3Patch           = "application/vnd.github.v3.patch"
 	mediaTypeOrgPermissionRepo = "application/vnd.github.v3.repository+json"
 
 	// Media Type values to access preview APIs
@@ -154,6 +156,22 @@ type UploadOptions struct {
 	Name string `url:"name,omitempty"`
 }
 
+// RawType represents type of raw format of a request instead of JSON.
+type RawType uint8
+
+const (
+	// Diff format.
+	Diff RawType = 1 + iota
+	// Patch format.
+	Patch
+)
+
+// RawOptions specifies parameters when user wants to get raw format of
+// a response instead of JSON.
+type RawOptions struct {
+	Type RawType
+}
+
 // addOptions adds the parameters in opt as URL query parameters to s.  opt
 // must be a struct whose fields may contain "url" tags.
 func addOptions(s string, opt interface{}) (string, error) {

github/pulls.go

@@ -6,6 +6,7 @@
 package github
 
 import (
+	"bytes"
 	"fmt"
 	"time"
 )
@@ -134,6 +135,32 @@ func (s *PullRequestsService) Get(owner string, repo string, number int) (*PullR
 	return pull, resp, err
 }
 
+// GetRaw gets raw (diff or patch) format of a pull request.
+func (s *PullRequestsService) GetRaw(owner string, repo string, number int, opt RawOptions) (string, *Response, error) {
+	u := fmt.Sprintf("repos/%v/%v/pulls/%d", owner, repo, number)
+	req, err := s.client.NewRequest("GET", u, nil)
+	if err != nil {
+		return "", nil, err
+	}
+
+	switch opt.Type {
+	case Diff:
+		req.Header.Set("Accept", mediaTypeV3Diff)
+	case Patch:
+		req.Header.Set("Accept", mediaTypeV3Patch)
+	default:
+		return "", nil, fmt.Errorf("unsupported raw type %d", opt.Type)
+	}
+
+	ret := new(bytes.Buffer)
+	resp, err := s.client.Do(req, ret)
+	if err != nil {
+		return "", resp, err
+	}
+
+	return ret.String(), resp, err
+}
+
 // NewPullRequest represents a new pull request to be created.
 type NewPullRequest struct {
 	Title *string `json:"title,omitempty"`

github/pulls_test.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"net/http"
 	"reflect"
+	"strings"
 	"testing"
 )
 
@@ -67,6 +68,61 @@ func TestPullRequestsService_Get(t *testing.T) {
 	}
 }
 
+func TestPullRequestService_GetRawDiff(t *testing.T) {
+	setup()
+	defer teardown()
+	const rawStr = "@@diff content"
+
+	mux.HandleFunc("/repos/o/r/pulls/1", func(w http.ResponseWriter, r *http.Request) {
+		testMethod(t, r, "GET")
+		testHeader(t, r, "Accept", mediaTypeV3Diff)
+		fmt.Fprint(w, rawStr)
+	})
+
+	ret, _, err := client.PullRequests.GetRaw("o", "r", 1, RawOptions{Diff})
+	if err != nil {
+		t.Fatalf("PullRequests.GetRaw returned error: %v", err)
+	}
+
+	if ret != rawStr {
+		t.Errorf("PullRequests.GetRaw returned %s want %s", ret, rawStr)
+	}
+}
+
+func TestPullRequestService_GetRawPatch(t *testing.T) {
+	setup()
+	defer teardown()
+	const rawStr = "@@patch content"
+
+	mux.HandleFunc("/repos/o/r/pulls/1", func(w http.ResponseWriter, r *http.Request) {
+		testMethod(t, r, "GET")
+		testHeader(t, r, "Accept", mediaTypeV3Patch)
+		fmt.Fprint(w, rawStr)
+	})
+
+	ret, _, err := client.PullRequests.GetRaw("o", "r", 1, RawOptions{Patch})
+	if err != nil {
+		t.Fatalf("PullRequests.GetRaw returned error: %v", err)
+	}
+
+	if ret != rawStr {
+		t.Errorf("PullRequests.GetRaw returned %s want %s", ret, rawStr)
+	}
+}
+
+func TestPullRequestService_GetRawInvalid(t *testing.T) {
+	setup()
+	defer teardown()
+
+	_, _, err := client.PullRequests.GetRaw("o", "r", 1, RawOptions{100})
+	if err == nil {
+		t.Fatal("PullRequests.GetRaw should return error")
+	}
+	if !strings.Contains(err.Error(), "unsupported raw type") {
+		t.Error("PullRequests.GetRaw should return unsupported raw type error")
+	}
+}
+
 func TestPullRequestsService_Get_headAndBase(t *testing.T) {
 	setup()
 	defer teardown()