  Numerous efforts have been invested in improving the effectiveness of bug
localization techniques, whereas little attention is paid to making these tools
run more efficiently in continuously evolving software repositories. This paper
first analyzes the information retrieval model behind a classic bug
localization tool, BugLocator, and builds a mathematical foundation
illustrating that the model can be updated incrementally when codebase or bug
reports evolve. Then, we present IncBL, a tool for Incremental Bug Localization
in evolving software repositories. IncBL is evaluated on the Bugzbook dataset,
and the results show that IncBL can significantly reduce the running time by
77.79% on average compared with the re-computing the model, while maintaining
the same level of accuracy. We also implement IncBL as a Github App that can be
easily integrated into open-source projects on GitHub. Users can deploy and use
IncBL locally as well. The demo video for IncBL can be viewed at
https://youtu.be/G4gMuvlJSb0, and the source code can be found at
https://github.com/soarsmu/IncBL.
