Add rust-toolchain.toml file (#6445)

* Add `rust-toolchain.toml` file

This file ensures that CI and all developers, by default, use the same Rust version. This helps reduce differences between e.g. `clippy` or `rustfmt` versions.

* renovatebot: Keep `rust-toolchain.toml` updated automatically

Author: Turbo87

.github/renovate.json5

@@ -11,6 +11,7 @@
         ":automergeTesters",
         "regexManagers:dockerfileVersions",
         "regexManagers:githubActionsVersions",
+        "github>Turbo87/renovate-config//rust/updateToolchain",
     ],
     "js": {
         "labels": ["A-frontend 🐹"],

.github/workflows/ci.yml

@@ -17,8 +17,6 @@ env:
   DIESEL_CLI_VERSION: 2.0.1
   # renovate: datasource=npm depName=pnpm
   PNPM_VERSION: 8.4.0
-  # renovate: datasource=github-releases depName=rust lookupName=rust-lang/rust
-  RUST_VERSION: 1.69.0
 
 jobs:
   changed-files:
@@ -54,6 +52,7 @@ jobs:
             Cargo.lock
             Cargo.toml
             RustConfig
+            rust-toolchain.toml
 
     outputs:
       non-js: ${{ steps.changed-files-non-js.outputs.any_modified }}
@@ -71,7 +70,6 @@ jobs:
     steps:
       - uses: actions/[email protected]
 
-      - run: rustup default ${{ env.RUST_VERSION }}
       - run: rustup component add rustfmt
       - run: rustup component add clippy
 
@@ -110,8 +108,6 @@ jobs:
     steps:
       - uses: actions/[email protected]
 
-      - run: rustup default ${{ env.RUST_VERSION }}
-
       - uses: Swatinem/[email protected]
 
       - run: cargo install diesel_cli --vers ${{ env.DIESEL_CLI_VERSION }} --no-default-features --features postgres --debug

rust-toolchain.toml

@@ -0,0 +1,2 @@
+[toolchain]
+channel = "1.69.0"