[RFC 0106] Nix release schedule

rfcs/0106-nix-release-schedule.md

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+---
+feature: Nix release schedule
+start-date: 2021-09-23
+author: Eelco Dolstra
+co-authors: (find a buddy later to help out with the RFC)
+shepherd-team: @Ericson2314, @regnat, @Ma27, @tomberek
+shepherd-leader: @tomberek
+related-issues: N/A
+---
+
+# Summary
+[summary]: #summary
+
+Do a new Nix release every 6 weeks.
+
+# Motivation
+[motivation]: #motivation
+
+The last major Nix release, 2.3, came out in September 2019. Since
+then, there has been a huge amount of work on the Nix master branch,
+including major improvements to the new command line interface and new
+experimental features such as flakes, the content-addressable Nix
+store, and recursive Nix. This forces many users to use unstable Nix
+releases, which is undesirable.
+
+In the future, we should avoid having such long gaps between releases,
+since it’s bad for both contributors and users that there is an
+unbounded amount of time before a new feature shows up in a stable
+release. The thing that has historically caused long gaps between Nix
+releases is new experimental features landing in master that we
+weren’t quite sure about, and doing a new release meant having to
+support these features indefinitely. However, Nix 2.4 introduces an
+experimental-features setting that enables us to add such features in
+a way that they can be changed or removed, while still getting
+feedback from adventurous users. So long as experimental features
+don’t cause breakage in stable features, it’s fine to merge them into
+master and include them in a new release.
+
+# Detailed design
+[design]: #detailed-design
+
+* We do a new Nix release (named 2.5.0, 2.6.0, 3.0.0, ...) every 6
+  weeks. The release process is already almost entirely automated so
+  this is pretty easy.
+
+* For each major release, we create a maintenance branch (named
+  e.g. `2.5-maintenance`) and corresponding Hydra jobset. Patch
+  releases (e.g. 2.5.1) are made as needed.
+
+* The master branch should be kept in a releasable state at all
+  times. This means that the jobset
+  https://hydra.nixos.org/jobset/nix/master should be completely
+  green.
+
+* PRs should include release notes, if applicable. (Currently trawling
+  through the history to dig up interesting stuff for the release
+  notes is the most work in making a new release.) The PR template
+  will be updated to reflect this.
+
+# Drawbacks
+[drawbacks]: #drawbacks
+
+Infrequent releases give somewhat more stability to users. Users of Nix-stable
+have been blissfully isolated from all the code churn on master for
+the last two years.
+
+# Alternatives
+[alternatives]: #alternatives
+
+Stick to the current release-when-it's-ready non-schedule.
+
+# Previous work
+
+[RFC 0009](https://github.com/NixOS/rfcs/pull/9) proposed a rapid
+release policy where releases can be done at any time (e.g. on
+request) rather than on a fixed schedule. It wasn't feasible at the
+time because we didn't have a notion of experimental features, so we
+had to give such features some time to stabilize before doing a new
+release.
+
+# Future work
+[future]: #future-work
+
+N/A