ci: check formatting of our Rust code

Introduce a CI check that verifies that our Rust code is well-formatted.
This check uses rustfmt(1), which is the de-facto standard in the Rust
world.

The rustfmt(1) tool allows to tweak the final format in theory. In
practice though, the Rust ecosystem has aligned on style "editions".
These editions only exist to ensure that any potential changes to the
style don't cause reformats to existing code bases. Other than that,
most Rust projects out there accept this default style of a specific
edition.

Let's do the same and use that default style. It may not be anyone's
favorite, but it is consistent and by making it part of our CI we also
enforce it right from the start.

Note that we don't have to pick a specific style edition here, as the
edition is automatically derived from the edition we have specified in
our "Cargo.toml" file.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

.github/workflows/main.yml

@@ -458,6 +458,21 @@ jobs:
     - run: ci/install-dependencies.sh
     - run: ci/run-static-analysis.sh
     - run: ci/check-directional-formatting.bash
+  rust-analysis:
+    needs: ci-config
+    if: needs.ci-config.outputs.enabled == 'yes'
+    env:
+      jobname: RustAnalysis
+      CI_JOB_IMAGE: ubuntu:rolling
+    runs-on: ubuntu-latest
+    container: ubuntu:rolling
+    concurrency:
+      group: rust-analysis-${{ github.ref }}
+      cancel-in-progress: ${{ needs.ci-config.outputs.skip_concurrent == 'yes' }}
+    steps:
+    - uses: actions/checkout@v4
+    - run: ci/install-dependencies.sh
+    - run: ci/run-rust-checks.sh
   sparse:
     needs: ci-config
     if: needs.ci-config.outputs.enabled == 'yes'

.gitlab-ci.yml

@@ -212,6 +212,17 @@ static-analysis:
     - ./ci/run-static-analysis.sh
     - ./ci/check-directional-formatting.bash
 
+rust-analysis:
+  image: ubuntu:rolling
+  stage: analyze
+  needs: [ ]
+  variables:
+    jobname: RustAnalysis
+  before_script:
+    - ./ci/install-dependencies.sh
+  script:
+    - ./ci/run-rust-checks.sh
+
 check-whitespace:
   image: ubuntu:latest
   stage: analyze

ci/install-dependencies.sh

@@ -126,6 +126,11 @@ StaticAnalysis)
 	sudo apt-get -q -y install coccinelle libcurl4-openssl-dev libssl-dev \
 		libexpat-dev gettext make
 	;;
+RustAnalysis)
+	sudo apt-get -q -y install rustup
+	rustup default stable
+	rustup component add rustfmt
+	;;
 sparse)
 	sudo apt-get -q -y install libssl-dev libcurl4-openssl-dev \
 		libexpat-dev gettext zlib1g-dev sparse

ci/run-rust-checks.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+. ${0%/*}/lib.sh
+
+set +x
+
+if ! group "Check Rust formatting" cargo fmt --all --check
+then
+	RET=1
+fi
+
+exit $RET