Corrective Commit Probability Code Quality Metric


An article signed by Idan Amit and Dror G. Feitelson from the Department of Computer Science at the Hebrew University of Jerusalem, presents a code quality metric, the Corrective Commit Probability (CCP).

This metric measures the probability that a commit reflects corrective maintenance. The authors think that this metric agrees with developers’ concept of quality, informative, and stable. Corrective commits are identified by applying a linguistic model to the commit messages. The  team compute the CCP of all large active GitHub projects (7,557 projects with 200+ com-mits in 2019). This leads to the creation of a quality scale, suggesting that the bottom 10% of quality projects spend at least 6 times more effort on fixing bugs than the top 10%. Analysis of project attributes shows that lower CCP (higher quality) is associated with smaller files, lower coupling, use of languages like JavaScript and C# as opposed to PHP and C++, fewer developers, lower developer churn, better on boarding, and  better  productivity. Among  other  things these results support the “Quality is Free” claim, and suggest that achieving higher quality need not require higher expenses.

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