fix(#130): cleanup and test improvements

- Fix extra blank lines between GetPullRequest and GetPullRequestFiles
- Add TestPostReview_CommitIDFromRequest to verify CommitID passes through

github/api_test.go

@@ -542,3 +542,41 @@ func TestDoRequestWithBody_RejectsHTTP(t *testing.T) {
 		t.Fatal("expected error for HTTP request")
 	}
 }
+
+func TestPostReview_CommitIDFromRequest(t *testing.T) {
+	const wantCommitID = "abc123def456"
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var payload postReviewRequest
+		if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
+			t.Errorf("decode body: %v", err)
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		if payload.CommitID != wantCommitID {
+			t.Errorf("commit_id = %q, want %q", payload.CommitID, wantCommitID)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(reviewResponse{
+			ID:       1,
+			Body:     payload.Body,
+			State:    "COMMENTED",
+			CommitID: payload.CommitID,
+			User:     struct{ Login string `json:"login"` }{Login: "rodin"},
+		})
+	}))
+	defer srv.Close()
+
+	c := NewClient("tok", srv.URL, AllowInsecureHTTPForTest())
+	review, err := c.PostReview(context.Background(), "owner", "repo", 1, vcs.ReviewRequest{
+		Body:     "looks good",
+		Event:    vcs.ReviewEventApprove,
+		CommitID: wantCommitID,
+	})
+	if err != nil {
+		t.Fatalf("PostReview: %v", err)
+	}
+	if review.CommitID != wantCommitID {
+		t.Errorf("review.CommitID = %q, want %q", review.CommitID, wantCommitID)
+	}
+}