[Nix-dev] Breaking changes log

[stewart mackenzie]

Ah indeed thank you for the correction. Though my suggestion is to
adopt C4 in its entirety. There would be no unstable master branch. At
all times there is only one branch, that being master, and the stable
APIs as part of this master branch remain stable, to be depricated and
eventually made into legacy. Topic branches are only on forks. In
effect we do a rolling release, with master being production ready at
all times. Ideally if we could have a similar rather explicit
stability annotation keyword syntax as demonstrated by rust-lang's
API, I'd be glowing.