From: Patrick Steinhardt Date: Mon, 08 Sep 2025 14:13:13 GMT Subject: [PATCH RFC v3 6/8] BreakingChanges: announce Rust becoming mandatory Message-ID: <20250908-b4-pks-rust-breaking-change-v3-6-1cd7189fed3b@pks.im> In-Reply-To: <20250908-b4-pks-rust-breaking-change-v3-0-1cd7189fed3b@pks.im> Over the last couple of years the appetite for bringin Rust into the codebase has grown significantly across the developer base. Introducing Rust is a major change though and has ramifications for the whole ecosystem: - Some platforms have a Rust toolchain available, but have not yet integrated it into their build infrastructure. - Some platforms don't have any support for Rust at all. - Some platforms may have to figure out how to fit Rust into their bootstrapping sequence. Due to this, and given that Git is a critical piece of infrastructure for the whole industry, we cannot just introduce such a heavyweight dependency without doing our due diligence. Instead, preceding commits have introduced a test balloon into our build infrastructure that convert one tiny subsystem to use Rust. For now, using Rust to build that subsystem is entirely optional -- if no Rust support is available, we continue to use the C implementation. This test balloon has the intention to give distributions time and let them ease into our adoption of Rust. Having multiple implementations of the same subsystem is not sustainable though, and the plan is to eventually be able to use Rust freely all across our codebase. As such, there is the intent to make Rust become a mandatory part of our build process. Add an announcement to our breaking changes that Rust will become mandatory in Git 3.0. A (very careful and non-binding) estimate might be that this major release might be released in the second half of next year, which should give distributors enough time to prepare for the change. Signed-off-by: Patrick Steinhardt --- Documentation/BreakingChanges.adoc | 41 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/Documentation/BreakingChanges.adoc b/Documentation/BreakingChanges.adoc index f8d2eba061..b6ae2241f8 100644 --- a/Documentation/BreakingChanges.adoc +++ b/Documentation/BreakingChanges.adoc @@ -165,6 +165,47 @@ A prerequisite for this change is that the ecosystem is ready to support the "reftable" format. Most importantly, alternative implementations of Git like JGit, libgit2 and Gitoxide need to support it. +* Git will require Rust as a mandatory part of the build process. While Git + already started to adopt Rust in Git 2.52, all parts written in Rust are + optional for the time being. This includes: ++ + ** Subsystems that have an alternative implementation in Rust to test + interoperability between our C and Rust codebase. + ** Newly written features that are not mission critical for a fully functional + Git client. ++ +These changes are meant as test balloons to allow distributors of Git to prepare +for Rust becoming a mandatory part of the build process. There will be multiple +milestones for the introduction of Rust: ++ +1. Initially, with Git 2.52, support for Rust will be auto-detected by Meson and + disabled in our Makefile so that the project can sort out the initial + infrastructure. +2. In Git 2.53, support for Rust will be enabled by default in case Git is + compiled with breaking changes. Breaking changes can be enabled for Meson by + saying `meson configure -Dbreaking_changes=true` and for Makefile-based + builds via `make WITH_BREAKING_CHANGES=YesPlease`. It will still be possible + to compile with breaking changes, but explicitly disable Rust. +3. In Git 2.54, both build systems will default-enable support for Rust even + when breaking changes aren't enabled. Consequently, builds will break by + default if Rust is not available on the build host. The use of Rust can still + be explicitly disabled via build flags. +4. In Git 3.0, the build options will be removed and support for Rust is + mandatory. ++ +You can explicitly ask both Meson and our Makefile-based system to enable Rust +by saying `meson configure -Drust=enabled` and `make WITH_RUST=YesPlease`, +respectively. ++ +The Git project will declare the last version before Git 3.0 to be a long-term +support release. This long-term release will receive important bug fixes for at +least four release cycles and security fixes for six release cycles. The Git +project will hand over maintainership of the long-term release to distributors +in case they need to extend the life of that long-term release even further. In +that case, the backporting process will be handled by these distributors, but +the backported patches will be reviewed on the mailing list and pulled in by the +Git maintainer. + === Removals * Support for grafting commits has long been superseded by git-replace(1). -- 2.51.0.417.g1ba7204a04.dirty