Although state-of-the-art software repositories based on versioning system information are useful to assess the evolution of a software system, the information they contain is limited in several ways. Versioning systems such as CVS or SubVersion store only snapshots of text files, leading to a loss of information: The exact sequence of changes between two versions is hard to recover. In this paper we present an alternative information repository which stores incremental changes to the system under study, retrieved from the IDE used to build the software. We then use this change-based model of system evolution to assess when refactorings happen in two case studies, and compare our findings with refactoring detection approaches on classical versioning system repositories.