core: Consolidate translation files (#1459)

* For core modules, consolidate their translation template into
  priv/translations/template/zotonic.pot, using msgcat.
* For core modules, consolidate their translations into
  priv/translations/(lang).po.
* Remove translation files from their old location inside the modules.
* Remove duplicate translations.
* Trim translation labels from templates.
* Extract translations labels as binaries to fix UTF-encoded labels from
  being skipped.
* Update Docker containers to include gettext package, which is
  required for msgmerge and msgcat.
* Update documentation.

.gitignore

@@ -28,6 +28,8 @@ deps/
 /priv/mnesia/
 /priv/sites/default/files/
 /priv/modules/
+/priv/translations/template/
+/priv/translations/zotonic.pot
 
 /modules/*/translations/template/*.pot
 

Dockerfile

@@ -12,7 +12,7 @@ RUN sed -f docker/erlang.config.sed priv/erlang.config.in > /etc/zotonic/erlang.
 # Note: dumb-init and gosu are pulled from edge; remove that when upgrading to an alpine release that
 # includes those packages.
 RUN apk add --virtual build-deps --no-cache ca-certificates wget curl make gcc musl-dev g++ bsd-compat-headers git \
-    && apk add --no-cache bash imagemagick \
+    && apk add --no-cache bash gettext imagemagick \
     && apk add --no-cache --repository http://dl-3.alpinelinux.org/alpine/edge/community/ dumb-init \
         erlang erlang-inets erlang-compiler erlang-crypto erlang-mnesia erlang-ssl erlang-stdlib erlang-public-key erlang-tools erlang-dev erlang-asn1 erlang-syntax-tools erlang-eunit erlang-parsetools erlang-snmp erlang-sasl erlang-xmerl erlang-erl-interface \
     && apk add --no-cache --repository http://dl-3.alpinelinux.org/alpine/edge/testing/ gosu \

Dockerfile.dev

@@ -8,7 +8,7 @@ WORKDIR /opt/zotonic
 
 RUN sed -f docker/erlang.config.sed priv/erlang.config.in > /etc/zotonic/erlang.config
 
-RUN apk add --no-cache ca-certificates bash curl make gcc musl-dev g++ bsd-compat-headers git imagemagick inotify-tools wget \
+RUN apk add --no-cache ca-certificates bash curl make gcc musl-dev g++ bsd-compat-headers gettext git imagemagick inotify-tools wget \
     && apk add --no-cache --repository http://dl-3.alpinelinux.org/alpine/edge/community/ \
         erlang erlang-inets erlang-compiler erlang-crypto erlang-mnesia erlang-ssl erlang-stdlib erlang-public-key erlang-tools erlang-dev erlang-asn1 erlang-syntax-tools erlang-eunit erlang-parsetools erlang-snmp erlang-sasl erlang-xmerl erlang-erl-interface
 

doc/developer-guide/translation.rst

@@ -78,16 +78,22 @@ Generation of translations
 
 The fixed texts in a Zotonic website are translated using the `GNU
 gettext <http://www.gnu.org/software/gettext/>`_ ``.po`` file format and
-its related tools.
+its related tools. If you’re not using our :ref:`guide-docker` images, you may
+have to install gettext first:
 
-In Zotonic, static translations are organized in each Zotonic
-module. It is the module’s responsibility to provide translations for
-all the texts that it uses in its templates. All files related to
-static translations live inside the ``translations/`` subdirectory of
-a module (remember: a Zotonic site is just a module!).
+.. code-block:: shell
 
-In the ``translations/`` directory of the modules you can find the ``.po``
-files containing the translations. They are marked with the their language code.  (Optionally you can name your file like:
+    $ sudo apt-get install gettext
+
+In Zotonic, translations files are placed in two locations:
+
+- for the core modules, the translation files are consolidated in
+  :file:`priv/translations/`;
+- third-party modules and sites, including your own, have their translation
+  files in a :file:`translations/` subdirectory in the module itself.
+
+In the translations directory you can find the ``.po`` files containing the
+translations. They are marked with the their language code. (Optionally you can name your file like:
 nl.foobar.po as Zotonic will only look at the part till the first '.'
 for the language code)::
 
@@ -102,15 +108,23 @@ for the language code)::
 This shows that module ``mod_foo`` has been translated into
 Dutch (`nl`), Turkish (`tr`) and Chinese traditional script (`zh-hant`).
 
-The template for translation strings is located in a ``.pot`` file, in ``mod_foo/translations/template/mod_foo.pot``. This pot file is regenerated when you click on the ‘Generate .pot files’ button on the Translation page in the admin. Alternatively,
+The ``.po`` translation files are based on translation templates (``.pot``
+files). The templates are located in :file:`translations/templates`:
+
+- :file:`priv/translations/template/zotonic.pot` for the core modules;
+- :file:`mod_foo/translations/template/mod_foo.pot` for custom modules.
+
+This ``.pot`` file is regenerated when you click on the ‘Generate .pot files’
+button on the :ref:`Translation page <mod_translation>` in the admin.
+Alternatively,
 from your Zotonic shell:
 
 .. code-block:: erlang
 
     mod_translation:generate(Context).
 
 Zotonic will parse all your templates and Erlang modules for translatable
-strings. These strings are then added to the .pot file.
+strings. These strings are then added to the ``.pot`` files.
 
 Creating a new translation for a module
 .......................................

doc/ref/installation/requirements.rst

@@ -26,6 +26,8 @@ installed:
 5. **git** Zotonic comes with a few subprojects which are pulled from
    the web with the ``git`` command.
 
+6. **gettext** For translation support.
+
 If you meet these requirements, head straight on to :ref:`guide-installation`,
 otherwise, read on below for the specifics on these.