The Impact of Version Control Operations on the Quality Change of the Source Code

The number of software systems under development and maintenance is rapidly increasing. The quality of a system’s source code tends to decrease during its lifetime which is a problem because maintaining low quality code consumes a big portion of the available efforts. In this research we investigated one aspect of code change, the version control commit operations (add, update, delete). We studied the impact of these operations on the maintainability of the code. We calculated the ISO/IEC 9126 quality attributes for thousands of revisions of an industrial and three open-source software systems. We also collected the cardinality of each version control operation type for every investigated revision. Based on these data, we identified that operation Add has a rather positive, while operation Update has a rather negative effect on the quality. On the other hand, for operation Delete we could not find a clear connection to quality change.