Add initial CI jobs for Rust build (#28)

* Modernize Rust syntax to 2018 edition and fix many lint warnings

* Correct full namespaces of imports
* Don't import things that aren't used (yet)
* Use `_` prefix for private / unused values (should be refactored back
  to regular names on a case by cases basis as they are used & made public)
* Order and space according to rustfmt

The bulk of this work was done by:

    cargo +nightly fix --edition

* Explicitly parse Rust as latest syntax edition (default is 2015)

* Fix coding style with `rustfmt`

* Correct bogus file extension, .rs → .sh

* Add CI jobs to lint, validate, build, & test Rust code

* Track Cargo lock file (this is correct Rust+VCS usage)

* Install GTK and libxcb devel headers into CI environment

.github/workflows/rust.yml

@@ -0,0 +1,100 @@
+name: Rust
+
+on:
+  pull_request: {}
+  push:
+    branches:
+      - master
+
+jobs:
+
+  build:
+    strategy:
+      fail-fast: false
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Fetch tags
+        run: git fetch --tags
+      - name: Setup system dependencies
+        run: sudo apt-get install libgtk-3-dev libxcb-shape0-dev libxcb-xfixes0-dev
+      - name: Install Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          override: true
+          components: clippy
+      - name: Cache cargo registry
+        uses: actions/cache@v1
+        with:
+          path: ~/.cargo/registry
+          key: build-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
+      - name: Cache cargo index
+        uses: actions/cache@v1
+        with:
+          path: ~/.cargo/git
+          key: build-cargo-index-${{ hashFiles('**/Cargo.lock') }}
+      - name: Cache cargo build
+        uses: actions/cache@v1
+        with:
+          path: target
+          key: build-cargo-build-target-${{ hashFiles('**/Cargo.lock') }}
+      - name: Run cargo build
+        run: |
+          cargo build --locked
+      - name: Run cargo test
+        run: |
+          cargo test --locked
+
+  rustfmt:
+    strategy:
+      fail-fast: false
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Install Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          override: true
+          components: rustfmt
+      - name: Run rustfmt
+        run: |
+          git ls-files '*.rs' | xargs rustfmt --check
+
+  cargo_bloat:
+    if: false
+    strategy:
+      fail-fast: false
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Install Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          override: true
+      - name: Cache cargo registry
+        uses: actions/cache@v1
+        with:
+          path: ~/.cargo/registry
+          key: bloat-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
+      - name: Cache cargo index
+        uses: actions/cache@v1
+        with:
+          path: ~/.cargo/git
+          key: bloat-cargo-index-${{ hashFiles('**/Cargo.lock') }}
+      - name: Cache cargo build
+        uses: actions/cache@v1
+        with:
+          path: target
+          key: bloat-cargo-build-target-${{ hashFiles('**/Cargo.lock') }}
+      - name: Run cargo bloat
+        uses: orf/cargo-bloat-action@v1
+        with:
+          token: ${{ github.token }}

.gitignore

@@ -1,3 +1,2 @@
 /target
-Cargo.lock
 *.swp