Although this is interesting, we should perhaps not hold a high degree of confidence in the results, because the methodology relies on the content of commit messages and the number of commits (if I read this correctly).

- The content of commit messages varies widely in expressiveness and meaningfulness, from 'Fix bug' to a detailed explanation. This confounds the classification of a commit.

- The number of commits can be very misleading depending on the committer's workflow. Some committers merge topic branches to include all their intermediate work in progress commits, which could overrepresent commits flagged as errors. Other committers rebase their topic branches into fewer, or even single, commits before merging. Or, some commits may fix multiple defects.

This kind of analysis is conceptually a worthy endeavor; it would be more meaningful if the metrics it employed were more strongly correlated with the attributes it was trying to analyze.