Address review feedback - require non-nil pull argument

Change-Id: Ibd502b7ab2d8e6bddda834e65529fa7f58141cc3

Author: gmlewis

github/pulls.go

@@ -198,23 +198,26 @@ type pullRequestUpdate struct {
 }
 
 // Edit a pull request.
-// pull may be nil, in which case the requested PR is returned unmodified.
+// pull must not be nil.
 //
 // 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(ctx context.Context, owner string, repo string, number int, pull *PullRequest) (*PullRequest, *Response, error) {
+	if pull == nil {
+		return nil, nil, fmt.Errorf("pull must be provided")
+	}
+
 	u := fmt.Sprintf("repos/%v/%v/pulls/%d", owner, repo, number)
 
-	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
-		}
+	update := &pullRequestUpdate{
+		Title: pull.Title,
+		Body:  pull.Body,
+		State: pull.State,
+	}
+	if pull.Base != nil {
+		update.Base = pull.Base.Ref
 	}
 
 	req, err := s.client.NewRequest("PATCH", u, update)

github/pulls_test.go

@@ -250,12 +250,6 @@ func TestPullRequestsService_Edit(t *testing.T) {
 			wantUpdate:   `{"title":"t"}`,
 			want:         &PullRequest{Number: Int(1)},
 		},
-		{
-			// nil request
-			sendResponse: `{}`,
-			wantUpdate:   `{}`,
-			want:         &PullRequest{},
-		},
 		{
 			// base update
 			input:        &PullRequest{Base: &PullRequestBranch{Ref: String("master")}},
@@ -293,7 +287,7 @@ func TestPullRequestsService_Edit(t *testing.T) {
 }
 
 func TestPullRequestsService_Edit_invalidOwner(t *testing.T) {
-	_, _, err := client.PullRequests.Edit(context.Background(), "%", "r", 1, nil)
+	_, _, err := client.PullRequests.Edit(context.Background(), "%", "r", 1, &PullRequest{})
 	testURLParseError(t, err)
 }