ci: check that jiff-cli generate doesn't produce diffs

This should help ensure that generated code doesn't get stale.

This is especially pertinent with the new `src/shared` module, which has
to be copied over to `crates/jiff-static/shared` any time a change is
made. Not all changes result in breakage (theoretical or otherwise), so
it's easy to forget to do.

.github/workflows/ci.yml

@@ -372,3 +372,50 @@ jobs:
     - name: Check formatting
       run: |
         cargo fmt --all -- --check
+
+  # Check that some `jiff-cli generate` commands don't produce a diff.
+  #
+  # This is useful for ensuring that, e.g., changes to `src/shared` are
+  # propagated to `crates/jiff-static/shared`.
+  generated:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v4
+    - name: Install Rust
+      uses: dtolnay/rust-toolchain@master
+      with:
+        toolchain: stable
+    - name: Install jiff-cli
+      run: cargo install -f --path crates/jiff-cli
+    - name: Generate code shared between jiff and jiff-static
+      run: |
+        jiff-cli generate shared
+        if ! git diff --exit-code; then
+          echo 'Please run `jiff-cli generated shared`'
+          exit 1
+        fi
+    - name: Generate crc32 code
+      run: |
+        jiff-cli generate crc32
+        if ! git diff --exit-code; then
+          echo 'Please run `jiff-cli generated crc32`'
+          exit 1
+        fi
+    - name: Generate unit designator match expression
+      run: |
+        jiff-cli generate unit-designator-match
+        if ! git diff --exit-code; then
+          echo 'Please run `jiff-cli generated unit-designator-match`'
+          exit 1
+        fi
+    - name: Generate mapping from Windows zones to IANA time zone identifiers
+      run: |
+        curl -LO 'https://raw.githubusercontent.com/unicode-org/cldr/main/common/supplemental/windowsZones.xml'
+        jiff-cli generate windows-zones windowsZones.xml
+        if ! git diff --exit-code; then
+          echo 'In a separate PR, please download windowsZones.xml'
+          echo 'from github.com/unicode-org/cldr and run'
+          echo '`jiff-cli generated windows-zones`'
+          exit 1
+        fi