One way I thought of doing this would be to just have every commit tagged with some subjective score given by the committer (in commit message), probably just 1

One way I thought of doing this would be to just have every commit tagged with some subjective score given by the committer (in commit message), probably just 1,2,3 to avoid too much weird subjectivity of a x/10 ranking, that gives how much the user subjectively thinks a commit is janky. then you will get a map of source code quality over time