[galaxy-dev] output name of downloaded datasets

Hello, My goal is to introduce, in the xml file of one tool like MACS for example, a supplementary command to redirect the output in another directory (+ creating link between this and the directory of galaxy outputs). But I want to rename my output with the same name that the downloading tools create in this way : GALAXY-NumOfDatasetInHistory[NameOfInput].bed And I don't find where this downloading tool is and so I don't find how create this name. Thanks. julie