Add Co-authored-by trailers to Merge's squash commit

internal/server/server.go

@@ -301,6 +301,21 @@ func (s *Server) GetUnmerged(w http.ResponseWriter, r *http.Request, taskID stri
 	})
 }
 
+func (s *Server) GetCoAuthors(w http.ResponseWriter, r *http.Request, taskID string) {
+	_, err := s.store.GetTask(r.Context(), taskID)
+	if err != nil {
+		writeStoreError(w, err)
+		return
+	}
+
+	coAuthors, err := s.agents.CoAuthors(r.Context(), taskID, actor(r))
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, coAuthors)
+}
+
 func (s *Server) MergeTask(w http.ResponseWriter, r *http.Request, taskID string) {
 	t, p, ok := s.activeTask(w, r, taskID)
 	if !ok {

internal/server/server_test.go

@@ -291,7 +291,17 @@ func TestMergeTask(t *testing.T) {
 	task := api.Task{}
 	h.do("POST", "/api/projects/"+p.Id+"/tasks", api.TaskCreate{Title: "Add notes"}, &task)
 
-	code := h.do("POST", "/api/tasks/"+task.Id+"/merge", nil, nil)
+	coAuthors := []api.Participant{}
+	code := h.do("GET", "/api/tasks/"+task.Id+"/co-authors", nil, &coAuthors)
+	if code != http.StatusOK || len(coAuthors) != 0 {
+		t.Fatalf("co-authors: %d %+v", code, coAuthors)
+	}
+	code = h.do("GET", "/api/tasks/nope/co-authors", nil, nil)
+	if code != http.StatusNotFound {
+		t.Fatalf("want 404 for co-authors of an unknown task, got %d", code)
+	}
+
+	code = h.do("POST", "/api/tasks/"+task.Id+"/merge", nil, nil)
 	if code != http.StatusBadRequest {
 		t.Fatalf("want 400 merging without a git identity, got %d", code)
 	}