Querying the History of Software Projects Using QWALKEKO

We present the QwalKeko meta-programming library for Clojure that enables querying the history of versioned software projects in a declarative manner. Unique to this library is its support for regular path expressions within history queries. Regular path expressions are akin to regular expressions, except that they match a sequence of successive snapshots of a software project along which user-specified logic conditions must hold. Such logic conditions can concern the source code within a snapshot, versioning information associated with the snapshot, as well as patterns of source code changes with respect to other snapshots. We have successfully used the resulting multi-faceted queries to detect refactorings in project histories. In this paper, we discuss how applicative logic meta-programming enabled combining the heterogenous components of QwalKeko into a uniform whole. We focus on the applicative logic interface to a new implementation of a well-known change distilling algorithm. We use the problem of detecting and categorizing changes made to Selenium-based test scripts for illustration purposes.