Add support for editing base branch of a PR. (#528)

As per the discussion in #421, the PullRequest parameter is converted into
an unexported type pullRequestUpdate which matches the shape expected by
the pulls PATCH endpoint.

Resolves #421.

Author: abhinav

github/pulls.go

@@ -189,12 +189,33 @@ func (s *PullRequestsService) Create(owner string, repo string, pull *NewPullReq
 	return p, resp, err
 }
 
+type pullRequestUpdate struct {
+	Title *string `json:"title,omitempty"`
+	Body  *string `json:"body,omitempty"`
+	State *string `json:"state,omitempty"`
+	Base  *string `json:"base,omitempty"`
+}
+
 // Edit a pull request.
 //
+// The following fields are editable: Title, Body, State, and Base.Ref.
+// Base.Ref updates the base branch of the pull request.
+//
 // GitHub API docs: https://developer.github.com/v3/pulls/#update-a-pull-request
 func (s *PullRequestsService) Edit(owner string, repo string, number int, pull *PullRequest) (*PullRequest, *Response, error) {
 	u := fmt.Sprintf("repos/%v/%v/pulls/%d", owner, repo, number)
-	req, err := s.client.NewRequest("PATCH", u, pull)
+
+	update := new(pullRequestUpdate)
+	if pull != nil {
+		update.Title = pull.Title
+		update.Body = pull.Body
+		update.State = pull.State
+		if pull.Base != nil {
+			update.Base = pull.Base.Ref
+		}
+	}
+
+	req, err := s.client.NewRequest("PATCH", u, update)
 	if err != nil {
 		return nil, nil, err
 	}

github/pulls_test.go

@@ -8,6 +8,7 @@ package github
 import (
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"reflect"
 	"strings"
@@ -235,28 +236,58 @@ func TestPullRequestsService_Edit(t *testing.T) {
 	setup()
 	defer teardown()
 
-	input := &PullRequest{Title: String("t")}
+	tests := []struct {
+		input        *PullRequest
+		sendResponse string
 
-	mux.HandleFunc("/repos/o/r/pulls/1", func(w http.ResponseWriter, r *http.Request) {
-		v := new(PullRequest)
-		json.NewDecoder(r.Body).Decode(v)
+		wantUpdate string
+		want       *PullRequest
+	}{
+		{
+			input:        &PullRequest{Title: String("t")},
+			sendResponse: `{"number":1}`,
+			wantUpdate:   `{"title":"t"}`,
+			want:         &PullRequest{Number: Int(1)},
+		},
+		{
+			// nil request
+			sendResponse: `{}`,
+			wantUpdate:   `{}`,
+			want:         &PullRequest{},
+		},
+		{
+			// base update
+			input:        &PullRequest{Base: &PullRequestBranch{Ref: String("master")}},
+			sendResponse: `{"number":1,"base":{"ref":"master"}}`,
+			wantUpdate:   `{"base":"master"}`,
+			want: &PullRequest{
+				Number: Int(1),
+				Base:   &PullRequestBranch{Ref: String("master")},
+			},
+		},
+	}
 
-		testMethod(t, r, "PATCH")
-		if !reflect.DeepEqual(v, input) {
-			t.Errorf("Request body = %+v, want %+v", v, input)
-		}
+	for i, tt := range tests {
+		madeRequest := false
+		mux.HandleFunc(fmt.Sprintf("/repos/o/r/pulls/%v", i), func(w http.ResponseWriter, r *http.Request) {
+			testMethod(t, r, "PATCH")
+			testBody(t, r, tt.wantUpdate+"\n")
+			io.WriteString(w, tt.sendResponse)
+			madeRequest = true
+		})
 
-		fmt.Fprint(w, `{"number":1}`)
-	})
+		pull, _, err := client.PullRequests.Edit("o", "r", i, tt.input)
+		if err != nil {
+			t.Errorf("%d: PullRequests.Edit returned error: %v", i, err)
+		}
 
-	pull, _, err := client.PullRequests.Edit("o", "r", 1, input)
-	if err != nil {
-		t.Errorf("PullRequests.Edit returned error: %v", err)
-	}
+		if !reflect.DeepEqual(pull, tt.want) {
+			t.Errorf("%d: PullRequests.Edit returned %+v, want %+v", i, pull, tt.want)
+		}
 
-	want := &PullRequest{Number: Int(1)}
-	if !reflect.DeepEqual(pull, want) {
-		t.Errorf("PullRequests.Edit returned %+v, want %+v", pull, want)
+		if !madeRequest {
+			t.Errorf("%d: PullRequest.Edit did not make the expected request", i)
+		}
 	}
 }