[PATCH v2 0/2] Use Rust in the Windows CI jobs

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

With v2.55.0, Git requires Rust by default, with an opt-out that is intended
to be dropped in one of the next versions.

Due to the special circumstances in the Windows part of the CI builds, each
Windows build job first downloads a "minimal Git for Windows SDK" that
contains the GCC toolchain required to build and test Git. As a consequence,
brian m. carlson opted out of Rust in Git's CI definition in 32d5b905909e
(Enable Rust by default, 2026-04-09).

So: How could we stop opting out? Notably, Rust is not part of that minimal
Git for Windows SDK, and including it would more than double that payload,
which I consider prohibitive. Yet including Rust in the minimal Git for
Windows SDK is not actually necessary, at least not for the GitHub workflow:
The runners on which this workflow is defined to run come with Rust
pre-installed.

Granted, this Rust installation is configured to target the Windows-native C
compiler, Visual C. To accommodate for the Windows CI job building with GCC,
this patch series adds a step to the workflow that ensures that the needed
Rust bits are installed and configured.

RFH: I haven't been able to confirm that GitLab's Windows runners come with
Rust preinstalled,
https://docs.gitlab.com/ci/runners/hosted_runners/windows/#available-runtimes
did not clarify that for me. Patrick (or anyone else with access to GitLab
CI), could you see whether this patch series builds on
saas-windows-medium-amd64 without need for further changes?

Changes since v1:

 * The inconsistency pointed out by Junio, that UCRT64 was once marked as
   using clang and once as using gcc was fixed by clarifying that UCRT64
   uses GCC.

Johannes Schindelin (2):
  rust: pick a GCC-compatible Cargo target under MSYS2/MinGW
  ci(windows): build with Rust

 .github/workflows/main.yml | 24 ++++++++++++++++++++++++
 Makefile                   |  3 ++-
 ci/lib.sh                  |  3 ---
 config.mak.uname           | 24 +++++++++++++++++++++++-
 4 files changed, 49 insertions(+), 5 deletions(-)


base-commit: f4742f3165d096130c39a71feb26374da37620f2
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2213%2Fdscho%2Fuse-rust-in-windows-ci-builds-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2213/dscho/use-rust-in-windows-ci-builds-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/2213

Range-diff vs v1:

 1:  2b7f58a037 = 1:  6567eceb32 rust: pick a GCC-compatible Cargo target under MSYS2/MinGW
 2:  7a24630fb9 ! 2:  07415393e5 ci(windows): build with Rust
     @@ Commit message
          linker) need to be installed; `rustup target add` alone is sufficient.
      
          Assisted-by: Claude Opus 4.7
     +    Helped-by: Junio C Hamano <gitster@pobox.com>
          Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
      
       ## .github/workflows/main.yml ##
     @@ .github/workflows/main.yml: jobs:
      +        CLANGARM64) target=aarch64-pc-windows-gnullvm ;;
      +        CLANG64)    target=x86_64-pc-windows-gnullvm  ;;
      +        CLANG32)    target=i686-pc-windows-gnullvm    ;;
     -+        UCRT64)     target=x86_64-pc-windows-gnullvm  ;;
     ++        UCRT64)     target=x86_64-pc-windows-gnu      ;;
      +        MINGW64)    target=x86_64-pc-windows-gnu      ;;
      +        MINGW32)    target=i686-pc-windows-gnu        ;;
      +        *) echo "::error::Unsupported MSYSTEM: $MSYSTEM"; exit 1 ;;

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