Earlier in the day, an early preview release for the next release of Git, 2.4-rc0, was tagged. Unlike many major releases in the past, this development cycle turned out to be relatively calm, fixing many usability warts and bugs, while introducing only a few new shiny toys.
In fact, the ratio of changes that are fixes and clean-ups in this release is unusually higher compared to recent releases. We keep a series of patches around each topic, whether it is a bugfix, a clean-up, or a new shiny toy, on its own topic branch, and each branch is merged to the 'master' branch after reviewing and testing, and then fixes and trivial clean-ups are also merged to the 'maint' branch. Because of this project structure, it is relatively easy to sift fixes and enhancement apart. Among new commits in release X since release (X-1), the ones that appear also in the last maintenance track for release (X-1) are fixes and clean-ups, while the remainder is enhancements.
Among the changes that went into v1.9.0 since v1.8.5, 23% of them were fixes that got merged to v18.104.22.168, for example, and this number has been more or less stable throughout the last year. Among the changes in v2.3.0 since v2.2.0, 18% of them were also in v2.2.2. Today's preview v2.4.0-rc0, however, has 333 changes since v2.3.0, among which 110 are in v2.3.4, which means that 33% of the changes are fixes and clean-ups.
These fixes came from 33 contributors in total, but changes from only a few usual suspects dominate and most other contributors have only one or two changes on the maintenance track. It is illuminating to compare the output between
$ git shortlog --no-merges -n -s ^maint v2.3.0..master
$ git shortlog --no-merges -n -s v2.3.0..maint
to see who prefers to work on new shiny toys and who works on product quality by fixing other people's bugs. The first command sorts the contributors by the number of commits since v2.3.0 that are only in the 'master', i.e. new shiny toys, and the second command sorts the contributors by the number of commits since v2.3.0 that are in the 'maint', i.e. fixes and clean-ups.
The output matches my perception (as the project maintainer, I at least look at, if not read carefully, all the changes) of each contributor's strength and weakness fairly well. Some are always looking for new and exciting things while being bad at tying loose ends, while others are more careful perfectionists.