I have read this in many project description - like here or here. Looking for an explanation of what this means, I simply get more pages that discuss a project's "Y-O-Y commits". What does thie metric mean? What is the use in reporting this metric?
They are using the metric of year-over-year commits to assess the health of a given open source project. They are looking at the most recent 12 months and comparing the number of commits to the number of commits to the next most recent 12 months and determining if the number of commits in the most recent 12 month window are about equal, significantly greater than, or significantly more than the commits in the older window.
I'm not aware of any studies that determine if it's a valid metric, but it doesn't seem that useful to me, especially given some of the caveats: it doesn't look at the number of individuals making commits or the lines of code changed. They also appear to look at the repository as a whole and perhaps not even source files.
It seems like a naive method to determine if a project is still active. If the commits in a 12 month span are equal to or greater than the previous 12 month span, then the project is active. However, a significant decline can indicate that the project is no longer maintained. I'm not sure that's valid, as any number of things may influence the number of commits, but not the maintenance of the project:
- the project is in a maintenance phase rather than active development
- different individual contributors may commit at different rates
- if using git, commits may or may not be squashed and this may change, making fewer commits visible