Why do your projects’ releases skip odd minor version numbers?
PrevNode LinkNextThis is what the "Producing OSS" book calls "The Even/Odd Strategy". Quoting from it ( under CC-by-sa ):
Some projects use the parity of the minor number component to indicate the stability of the software: even means stable, odd means unstable. This applies only to the minor number, not the major or micro numbers. Increments in the micro number still indicate bug fixes (no new features), and increments in the major number still indicate big changes, new feature sets, etc.
The advantage of the even/odd system, which has been used by the Linux kernel project[78] among others, is that it offers a way to release new functionality for testing without subjecting production users to potentially unstable code. People can see from the numbers that "2.4.21" is okay to install on their live web server, but that "2.5.1" should probably stay confined to home workstation experiments. The development team handles the bug reports that come in from the unstable (odd-minor-numbered) series, and when things start to settle down after some number of micro releases in that series, they increment the minor number (thus making it even), reset the micro number back to "0", and release a presumably stable package.
This system preserves, or at least, does not conflict with, the compatibility guidelines given earlier. It simply overloads the minor number with some extra information. This forces the minor number to be incremented about twice as often as would otherwise be necessary, but there's no real harm in that. The even/odd system is probably best for projects that have very long release cycles, and which by their nature have a high proportion of conservative users who value stability above new features. It is not the only way to get new functionality tested in the wild, however. In the section called “Stabilizing a Release” we will examine another, perhaps more common, method of releasing potentially unstable code to the public, in which the release number is further marked so that people have an idea of the risk/benefit trade-offs immediately on seeing the release's name.