fix: don't show private forks in forks list

- If a repository is forked to a private or limited user/organization,
the fork should not be visible in the list of forks depending on the
doer requesting the list of forks.
- Added integration testing for web and API route.

tests/integration/api_fork_test.go

@@ -17,6 +17,8 @@ import (
 	"code.gitea.io/gitea/modules/test"
 	"code.gitea.io/gitea/routers"
 	"code.gitea.io/gitea/tests"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestAPIForkAsAdminIgnoringLimits(t *testing.T) {
@@ -106,3 +108,44 @@ func TestAPIDisabledForkRepo(t *testing.T) {
 		session.MakeRequest(t, req, http.StatusNotFound)
 	})
 }
+
+func TestAPIForkListPrivateRepo(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	session := loginUser(t, "user5")
+	token := getTokenForLoggedInUser(t, session,
+		auth_model.AccessTokenScopeWriteRepository,
+		auth_model.AccessTokenScopeWriteOrganization)
+	org23 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 23, Visibility: api.VisibleTypePrivate})
+
+	req := NewRequestWithJSON(t, "POST", "/api/v1/repos/user2/repo1/forks", &api.CreateForkOption{
+		Organization: &org23.Name,
+	}).AddTokenAuth(token)
+	MakeRequest(t, req, http.StatusAccepted)
+
+	t.Run("Anomynous", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+
+		req := NewRequest(t, "GET", "/api/v1/repos/user2/repo1/forks")
+		resp := MakeRequest(t, req, http.StatusOK)
+
+		var forks []*api.Repository
+		DecodeJSON(t, resp, &forks)
+
+		assert.Empty(t, forks)
+		assert.EqualValues(t, "0", resp.Header().Get("X-Total-Count"))
+	})
+
+	t.Run("Logged in", func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
+
+		req := NewRequest(t, "GET", "/api/v1/repos/user2/repo1/forks").AddTokenAuth(token)
+		resp := MakeRequest(t, req, http.StatusOK)
+
+		var forks []*api.Repository
+		DecodeJSON(t, resp, &forks)
+
+		assert.Len(t, forks, 1)
+		assert.EqualValues(t, "1", resp.Header().Get("X-Total-Count"))
+	})
+}