Test extracting text from multiple books

This expands our testing to test extracting text from both the Rust
Book and Comprehensive Rust. We only check the format of the generated
POT file right now, but we might be able to expand this to other
checks later.

Author: mgeisler

.github/workflows/test.yml

@@ -25,12 +25,21 @@ jobs:
       - name: Test
         run: cargo test
 
-  rust-book:
-    name: Test with Rust Book
+  test-other-books:
+    strategy:
+      matrix:
+        include:
+          # Update the refs below once in a while.
+          - repo: rust-lang/book
+            ref: 5b6c1ceaa62ecbd6caef08df39b33b3938e99deb
+          - repo: google/comprehensive-rust
+            ref: 0dfd087538ed4b52cf30cafb3b9add49cd6d204a
+
+    name: Test with ${{ matrix.repo }}
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - uses: Swatinem/rust-cache@v2
         with:
@@ -43,17 +52,15 @@ jobs:
           cargo install --debug --path i18n-helpers
           cargo install --debug --locked --version 0.4.35 mdbook
 
-      - name: Checkout Rust Book
+      - name: Checkout ${{ matrix.repo }}
         uses: actions/checkout@v4
         with:
-          repository: rust-lang/book
-          # Update the commit hash once in a while to test newer
-          # versions.
-          ref: 5b6c1ceaa62ecbd6caef08df39b33b3938e99deb
-          path: rust-book
-
-      - name: Test extracting text from Rust Book
-        working-directory: rust-book
+          repository: ${{ matrix.repo }}
+          ref: ${{ matrix.ref }}
+          path: example-book
+
+      - name: Test extracting text
+        working-directory: example-book
         run: |
           MDBOOK_OUTPUT='{"xgettext": {"pot-file": "messages.pot"}}' mdbook build -d po
           msgfmt -o /dev/null --statistics po/messages.pot