Diff translations on every PR (#2214)

This uses a new mode of `i18n-report` to summarise the differences in
translations as an action on each PR.

.github/workflows/build.yml

@@ -162,3 +162,27 @@ jobs:
         env:
           MDBOOK_BOOK__LANGUAGE: ${{ matrix.language }}
         run: mdbook test
+
+  po-diff:
+    name: Translation diff
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup Rust cache
+        uses: ./.github/workflows/setup-rust-cache
+
+      - name: Install mdbook
+        uses: ./.github/workflows/install-mdbook
+
+      - name: Copy latest version of translations
+        run: cp -r po old-po
+
+      - name: Checkout base version
+        run: git checkout ${{ github.event.pull_request.base.sha }}
+
+      - name: Translation diff
+        run: i18n-report diff old-po/ po/ > $GITHUB_STEP_SUMMARY

.github/workflows/install-mdbook/action.yml

@@ -29,7 +29,7 @@ runs:
       shell: bash
 
     - name: Install i18n-report
-      run: cargo install i18n-report --locked --version 0.1.0
+      run: cargo install i18n-report --locked --version 0.2.0
       shell: bash
 
     - name: Install mdbook-exerciser

.github/workflows/publish.yml

@@ -55,14 +55,14 @@ jobs:
           done
 
       - name: Build translation report
-        run: i18n-report book/html/translation-report.html po/*.po
+        run: i18n-report report book/html/translation-report.html po/*.po
 
       - name: Build synced translation report
         run: |
           cp -r po synced-po
           MDBOOK_OUTPUT='{"xgettext": {"pot-file": "messages.pot", "granularity": 0}}' mdbook build -d synced-po
           for file in synced-po/*.po; do msgmerge --update $file synced-po/messages.pot ; done
-          i18n-report book/html/synced-translation-report.html synced-po/*.po
+          i18n-report report book/html/synced-translation-report.html synced-po/*.po
 
       - name: Setup Pages
         uses: actions/configure-pages@v5