l10n: README: document "core translation"

[thirdparty/git.git] / po / README.md

Core GIT Translations
=====================

This directory holds the translations for the core of Git. This document
describes how you can contribute to the effort of enhancing the language
coverage and maintaining the translation.

The localization (l10n) coordinator, Jiang Xin <worldhello.net@gmail.com>,
coordinates our localization effort in the l10 coordinator repository:

        https://github.com/git-l10n/git-po/

The two character language translation codes are defined by ISO_639-1, as
stated in the gettext(1) full manual, appendix A.1, Usual Language Codes.


Contributing to an existing translation
---------------------------------------
As a contributor for a language XX, you should first check TEAMS file in
this directory to see whether a dedicated repository for your language XX
exists. Fork the dedicated repository and start to work if it exists.

Sometime, contributors may find that the translations of their Git
distributions are quite different with the translations of the
corresponding version from Git official. This is because some Git
distributions (such as from Ubuntu, etc.) have their own l10n workflow.
For this case, wrong translations should be reported and fixed through
their workflows.


Creating a new language translation
-----------------------------------
If you are the first contributor for the language XX, please fork this
repository, prepare and/or update the translated message file po/XX.po
(described later), and ask the l10n coordinator to pull your work.

If there are multiple contributors for the same language, please first
coordinate among yourselves and nominate the team leader for your
language, so that the l10n coordinator only needs to interact with one
person per language.


Core translation
----------------
The core translation is the smallest set of work that must be completed
for a new language translation. Because there are more than 5000 messages
in the template message file "po/git.pot" that need to be translated,
this is not a piece of cake for the contributor for a new language.

The core template message file which contains a small set of messages
will be generated in "po-core/core.pot" automatically by running a helper
program named "git-po-helper" (described later).

    git-po-helper init --core XX.po

After translating the generated "po-core/XX.po", you can merge it to
"po/XX.po" using the following commands:

    msgcat po-core/XX.po po/XX.po -s -o /tmp/XX.po
    mv /tmp/XX.po po/XX.po
    git-po-helper update XX.po

Edit "po/XX.po" by hand to fix "fuzzy" messages, which may have misplaced
translated messages and duplicate messages.


Translation Process Flow
------------------------
The overall data-flow looks like this:

    +-------------------+            +------------------+
    | Git source code   | ---(1)---> | L10n coordinator |
    | repository        | <---(4)--- | repository       |
    +-------------------+            +------------------+
                                          |      ^
                                         (2)    (3)
                                          V      |
                                     +------------------+
                                     | Language Team XX |
                                     +------------------+

 * Translatable strings are marked in the source file.
 * L10n coordinator pulls from the source (1)
 * L10n coordinator updates the message template po/git.pot
 * Language team pulls from L10n coordinator (2)
 * Language team updates the message file po/XX.po
 * L10n coordinator pulls from Language team (3)
 * L10n coordinator asks the result to be pulled (4).


Maintaining the po/git.pot file
-------------------------------

(This is done by the l10n coordinator).

The po/git.pot file contains a message catalog extracted from Git's
sources. The l10n coordinator maintains it by adding new translations with
msginit(1), or update existing ones with msgmerge(1).  In order to update
the Git sources to extract the messages from, the l10n coordinator is
expected to pull from the main git repository at strategic point in
history (e.g. when a major release and release candidates are tagged),
and then run "make pot" at the top-level directory.

Language contributors use this file to prepare translations for their
language, but they are not expected to modify it.


Initializing a XX.po file
-------------------------

(This is done by the language teams).

If your language XX does not have translated message file po/XX.po yet,
you add a translation for the first time by running:

    msginit --locale=XX

in the po/ directory, where XX is the locale, e.g. "de", "is", "pt_BR",
"zh_CN", etc.

Then edit the automatically generated copyright info in your new XX.po
to be correct, e.g. for Icelandic:

    @@ -1,6 +1,6 @@
    -# Icelandic translations for PACKAGE package.
    -# Copyright (C) 2010 THE PACKAGE'S COPYRIGHT HOLDER
    -# This file is distributed under the same license as the PACKAGE package.
    +# Icelandic translations for Git.
    +# Copyright (C) 2010 Ævar Arnfjörð Bjarmason <avarab@gmail.com>
    +# This file is distributed under the same license as the Git package.
     # Ævar Arnfjörð Bjarmason <avarab@gmail.com>, 2010.

And change references to PACKAGE VERSION in the PO Header Entry to
just "Git":

    perl -pi -e 's/(?<="Project-Id-Version: )PACKAGE VERSION/Git/' XX.po

Once you are done testing the translation (see below), commit the result
and ask the l10n coordinator to pull from you.


Updating a XX.po file
---------------------

(This is done by the language teams).

If you are replacing translation strings in an existing XX.po file to
improve the translation, just edit the file.

If there's an existing XX.po file for your language, but the repository
of the l10n coordinator has newer po/git.pot file, you would need to first
pull from the l10n coordinator (see the beginning of this document for its
URL), and then update the existing translation by running:

    msgmerge --add-location --backup=off -U XX.po git.pot

in the po/ directory, where XX.po is the file you want to update.

Once you are done testing the translation (see below), commit the result
and ask the l10n coordinator to pull from you.


Testing your changes
--------------------

(This is done by the language teams, after creating or updating XX.po file).

Before you submit your changes go back to the top-level and do:

    make

On systems with GNU gettext (i.e. not Solaris) this will compile your
changed PO file with `msgfmt --check`, the --check option flags many
common errors, e.g. missing printf format strings, or translated
messages that deviate from the originals in whether they begin/end
with a newline or not.


Marking strings for translation
-------------------------------

(This is done by the core developers).

Before strings can be translated they first have to be marked for
translation.

Git uses an internationalization interface that wraps the system's
gettext library, so most of the advice in your gettext documentation
(on GNU systems `info gettext` in a terminal) applies.

General advice:

 - Don't mark everything for translation, only strings which will be
   read by humans (the porcelain interface) should be translated.

   The output from Git's plumbing utilities will primarily be read by
   programs and would break scripts under non-C locales if it was
   translated. Plumbing strings should not be translated, since
   they're part of Git's API.

 - Adjust the strings so that they're easy to translate. Most of the
   advice in `info '(gettext)Preparing Strings'` applies here.

 - If something is unclear or ambiguous you can use a "TRANSLATORS"
   comment to tell the translators what to make of it. These will be
   extracted by xgettext(1) and put in the po/*.po files, e.g. from
   git-am.sh:

       # TRANSLATORS: Make sure to include [y], [n], [e], [v] and [a]
       # in your translation. The program will only accept English
       # input at this point.
       gettext "Apply? [y]es/[n]o/[e]dit/[v]iew patch/[a]ccept all "

   Or in C, from builtin/revert.c:

       /* TRANSLATORS: %s will be "revert" or "cherry-pick" */
       die(_("%s: Unable to write new index file"), action_name(opts));

We provide wrappers for C, Shell and Perl programs. Here's how they're
used:

C:

 - Include builtin.h at the top, it'll pull in gettext.h, which
   defines the gettext interface. Consult with the list if you need to
   use gettext.h directly.

 - The C interface is a subset of the normal GNU gettext
   interface. We currently export these functions:

   - _()

    Mark and translate a string. E.g.:

        printf(_("HEAD is now at %s"), hex);

   - Q_()

    Mark and translate a plural string. E.g.:

        printf(Q_("%d commit", "%d commits", number_of_commits));

    This is just a wrapper for the ngettext() function.

   - N_()

    A no-op pass-through macro for marking strings inside static
    initializations, e.g.:

        static const char *reset_type_names[] = {
            N_("mixed"), N_("soft"), N_("hard"), N_("merge"), N_("keep"), NULL
        };

    And then, later:

        die(_("%s reset is not allowed in a bare repository"),
               _(reset_type_names[reset_type]));

    Here _() couldn't have statically determined what the translation
    string will be, but since it was already marked for translation
    with N_() the look-up in the message catalog will succeed.

Shell:

 - The Git gettext shell interface is just a wrapper for
   gettext.sh. Import it right after git-sh-setup like this:

       . git-sh-setup
       . git-sh-i18n

   And then use the gettext or eval_gettext functions:

       # For constant interface messages:
       gettext "A message for the user"; echo

       # To interpolate variables:
       details="oh noes"
       eval_gettext "An error occurred: \$details"; echo

   In addition we have wrappers for messages that end with a trailing
   newline. I.e. you could write the above as:

       # For constant interface messages:
       gettextln "A message for the user"

       # To interpolate variables:
       details="oh noes"
       eval_gettextln "An error occurred: \$details"

   More documentation about the interface is available in the GNU info
   page: `info '(gettext)sh'`. Looking at git-am.sh (the first shell
   command to be translated) for examples is also useful:

       git log --reverse -p --grep=i18n git-am.sh

Perl:

 - The Git::I18N module provides a limited subset of the
   Locale::Messages functionality, e.g.:

       use Git::I18N;
       print __("Welcome to Git!\n");
       printf __("The following error occurred: %s\n"), $error;

   Run `perldoc perl/Git/I18N.pm` for more info.


Testing marked strings
----------------------

Git's tests are run under LANG=C LC_ALL=C. So the tests do not need be
changed to account for translations as they're added.


PO helper
---------

To make the maintenance of XX.po easier, the l10n coordinator and l10n
team leaders can use a helper program named "git-po-helper". It is a
wrapper to gettext suite, specifically written for the purpose of Git
l10n workflow.

To build and install the helper program from source, see
[git-po-helper/README][].

Usage for git-po-helper:

  - To start a new language translation:

        git-po-helper init XX.po

  - To update your XX.po file:

        git-po-helper update XX.po

  - To check commit log and syntax of XX.po:

        git-po-helper check-po XX.po
        git-po-helper check-commits

Run "git-po-helper" without arguments to show usage.

[git-po-helper/README]: https://github.com/git-l10n/git-po-helper#readme