Add form-fetch-action to some forms, fix "fetch action" resp bug (#37305)

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/integration/editor_test.go

@@ -372,7 +372,8 @@ func testForkToEditFile(t *testing.T, session *TestSession, user, owner, repo, b
 				"action":    "convert_fork",
 			},
 		)
-		session.MakeRequest(t, req, http.StatusSeeOther)
+		resp = session.MakeRequest(t, req, http.StatusOK)
+		assert.NotNil(t, test.ParseJSONRedirect(resp.Body.Bytes()).Redirect)
 	})
 
 	// Fork repository again, and check the existence of the forked repo with unique name