[1/n] [ci] update MSRV and test on it, add clippy, fix clippy warnings (#70)

Clippy flagged an outdated MSRV -- update to the version currently in Omicron,
and add CI for the various permutations.

Also allow `/target` to be a symlink -- this is the setup I use.

Author: sunshowers

.github/workflows/rust.yml

@@ -3,11 +3,15 @@
 #
 name: Rust
 
+env:
+  RUSTFLAGS: -D warnings
+
 on:
   push:
     branches: [ main ]
   pull_request:
-    branches: [ main ]
+    # Allow CI to run on all PRs, not just ones targeting main. This allows
+    # stacked PRs to be tested.
 
 jobs:
   check-style:
@@ -22,15 +26,22 @@ jobs:
         components: rustfmt
     - name: Check style
       run: cargo fmt -- --check
+    - name: Check clippy
+      run: cargo clippy --all-targets --all-features
 
   build-and-test:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
+        # 1.81 is the MSRV.
+        toolchain: [ stable, "1.81" ]
         os: [ ubuntu-latest, macos-latest ]
     steps:
     # actions/checkout@v2
     - uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938
+    - uses: dtolnay/rust-toolchain@v1
+      with:
+        toolchain: ${{ matrix.toolchain }}
     - name: Build
       run: cargo build --tests --verbose
     - name: Run tests

.gitignore

@@ -1,6 +1,6 @@
 # Generated by Cargo
 # will have compiled files and executables
-/target/
+/target
 
 # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
 # More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html

Cargo.toml

@@ -3,11 +3,7 @@ name = "omicron-zone-package"
 version = "0.11.1"
 authors = ["Sean Klein <[email protected]>"]
 edition = "2021"
-#
-# Report a specific error in the case that the toolchain is too old for
-# let-else:
-#
-rust-version = "1.65.0"
+rust-version = "1.81.0"
 license = "MPL-2.0"
 repository = "https://github.com/oxidecomputer/omicron-package"
 description = "Packaging tools for Oxide's control plane software"

src/config.rs

@@ -113,7 +113,6 @@ impl Config {
             self.packages
                 .iter()
                 .filter(|(_, pkg)| target.includes_package(pkg))
-                .map(|(name, pkg)| (name, pkg))
                 .collect(),
         )
     }

src/package.rs

@@ -215,7 +215,7 @@ pub struct BuildConfig<'a> {
 static DEFAULT_TARGET: Target = Target(BTreeMap::new());
 static DEFAULT_PROGRESS: NoProgress = NoProgress::new();
 
-impl<'a> Default for BuildConfig<'a> {
+impl Default for BuildConfig<'_> {
     fn default() -> Self {
         Self {
             target: &DEFAULT_TARGET,