Sync src/ with date in PO file when publishing

Before, we always used the latest English source files when
publishing. This means that translations become outdated as soon as
anything is changed in the source.

This PR changes will instead freeze translations in place: they will
keep using the same English source files until a new POT file is
merged into the translation. We do this by relying on the
POT-Creation-Date field in the PO files.

We still update all the files around the Markdown files: this allows
us to fix things in the theme, for example.

Part of google/mdbook-i18n-helpers#16. The
logic here should eventually be moved to somewhere in
mdbook-i18n-helpers, most likely to the renderer that @sakex is
building in google/mdbook-i18n-helpers#84.

.github/workflows/publish.yml

@@ -23,13 +23,13 @@ env:
 
 jobs:
   publish:
-    environment:
-      name: github-pages
-      url: ${{ steps.deployment.outputs.page_url }}
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v3
+#        with:
+          # We need the full history for the restore commands below.
+ #         fetch-depth: 0
 
       - name: Setup Rust cache
         uses: ./.github/workflows/setup-rust-cache
@@ -47,8 +47,20 @@ jobs:
         run: |
           for po_lang in ${{ env.LANGUAGES }}; do
               echo "::group::Building $po_lang translation"
+              POT_CREATION_DATE=$(grep --max-count 1 '^"POT-Creation-Date:' po/$po_lang.po | sed -E 's/".*: (.*)\\n"/\1/')
+              if [[ $POT_CREATION_DATE == "" ]]; then
+                  POT_CREATION_DATE=now
+              fi
+              echo "Building $po_lang translation as of $POT_CREATION_DATE"
+              rm -r src/
+              git restore --source $(git rev-list -n 1 --before "$POT_CREATION_DATE" @) src/
+
+              # Set language and adjust URL. Clear the redirects since
+              # they are in sync with the source files, not the
+              # translation.
               MDBOOK_BOOK__LANGUAGE=$po_lang \
               MDBOOK_OUTPUT__HTML__SITE_URL=/comprehensive-rust/$po_lang/ \
+              MDBOOK_OUTPUT__HTML__REDIRECT='{}' \
               mdbook build -d book/$po_lang
               (cd book/$po_lang/exerciser && zip --recurse-paths ../html/comprehensive-rust-exercises.zip comprehensive-rust-exercises/)
               mv book/$po_lang/html book/html/$po_lang

po/bn.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-05\n"
 "PO-Revision-Date: \n"
 "Last-Translator: Md. Rasel Mandol <[email protected]>\n"
 "Language-Team: noob_rasel<[email protected]>\n"

po/da.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-24\n"
 "PO-Revision-Date: \n"
 "Last-Translator: \n"
 "Language-Team: \n"

po/de.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-19\n"
 "PO-Revision-Date: \n"
 "Last-Translator: \n"
 "Language-Team: \n"

po/el.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-08-26\n"
 "PO-Revision-Date: 2023-08-25 13:24-0700\n"
 "Last-Translator: root <[email protected]>\n"
 "Language-Team: Greek <[email protected]>\n"

po/es.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-11\n"
 "PO-Revision-Date: \n"
 "Last-Translator: \n"
 "Language-Team: \n"

po/fa.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-08-23\n"
 "PO-Revision-Date: 2023-08-08 21:41+0330\n"
 "Last-Translator: danny <[email protected]>\n"
 "Language-Team: Persian\n"

po/fr.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-17\n"
 "PO-Revision-Date: 2023-09-12 14:14-0400\n"
 "Last-Translator: Olivier Charrez <[email protected]>\n"
 "Language-Team: French <[email protected]>\n"

po/id.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-08-26\n"
 "PO-Revision-Date: 2023-08-25 14:03-0700\n"
 "Last-Translator: Aji Prio Sejati <[email protected]>\n"
 "Language-Team: Indonesian <[email protected]>\n"

po/it.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-19\n"
 "PO-Revision-Date: 2023-09-19 09:35+0100\n"
 "Last-Translator: Ivan De Marino <[email protected]>\n"
 "Language-Team: \n"

po/ja.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-24\n"
 "PO-Revision-Date: 2023-06-06 13:18+0900\n"
 "Last-Translator: Kenta Aratani <[email protected]>\n"
 "Language-Team: Japanese <[email protected]>\n"

po/ko.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: [한국어]Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-24\n"
 "PO-Revision-Date: \n"
 "Last-Translator: \n"
 "Language-Team: \n"

po/pl.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-08-26\n"
 "PO-Revision-Date: 2023-08-25 14:19-0700\n"
 "Last-Translator: Kuba Jaroszewski <[email protected]>\n"
 "Language-Team: Polish <[email protected]>\n"

po/pt-BR.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-08-28\n"
 "PO-Revision-Date: 2023-08-25 09:32-0700\n"
 "Last-Translator: \n"
 "Language-Team: \n"

po/ru.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-08\n"
 "PO-Revision-Date: 2023-08-25 14:28-0700\n"
 "Last-Translator: Yauheni Baltukha <[email protected]>\n"
 "Language-Team: \n"

po/tr.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-08-26\n"
 "PO-Revision-Date: 2023-08-25 14:48-0700\n"
 "Last-Translator: [email protected]\n"
 "Language-Team: Turkish <[email protected]>\n"

po/uk.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-19\n"
 "PO-Revision-Date: 2023-09-12 22:06+0000\n"
 "Last-Translator: Andrew Kushyk <[email protected]>\n"
 "Language-Team: \n"

po/zh-CN.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-09-18\n"
 "PO-Revision-Date: 2023-06-12 21:28-0700\n"
 "Last-Translator: Zhengping Jiang <[email protected]>\n"
 "Language-Team: Language zh-Hans\n"

po/zh-TW.po

@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Comprehensive Rust 🦀\n"
-"POT-Creation-Date: \n"
+"POT-Creation-Date: 2023-08-23\n"
 "PO-Revision-Date: 2023-06-02 14:43+0800\n"
 "Last-Translator: Hank Chen <[email protected]>\n"
 "Language-Team: Traditional Chinese (Taiwan) <[email protected]>\n"