On Automatic Summarization of What and Why Information in Source Code Changes

Accurate and complete commit messages summarizing software changes are important to support various software maintenance activities. In practice, these commit messages are often manually submitted by individual software developer to provide information about the changes involved in the incremental changes. Hence, the content and quality of these commit messages may be different. For example, some commit messages are too short and lack of essential information while others with too much detailed information can be time-consuming to read. What's more, most of the commit messages focus on what has been changed by developers in a commit, but why they changed and the motivation behind the code changes (which can assist developers in understanding code changes), are usually ignored. In this paper, we present an approach that can automatically generate the commit messages related to the code changes, including not only what have been changed but also why they were changed. Our approach uses method stereotypes and the type of changes to generate commit messages. We evaluate our approach by comparing the quality of generated messages with the original commit messages written by the original developers and those generated by a state-of-art technique, i.e., ChangeScribe. The results demonstrate that the messages generated by our approach are preferred in about 69% of the cases.