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Thomas De Schampheleire

ssh: set a valid locale in the ssh-serve process

In the SSH client configuration, the setting 'SendEnv' could contain variables
like 'LANG', 'LC_ALL', and others. This causes these environment variables
(with their values at the client-side) to be set in the server. However, not
every locale setting valid in the client, is also valid on the server.

This could lead to the error:
'locale.Error: unsupported locale setting'
when 'from mercurial import archival, merge as hg_merge, patch, ui' is
called.

Fix this problem by providing an ini setting 'ssh_locale' that the user can
set correctly, and which will be used to set LC_ALL and LANGUAGE in the
'kallithea-cli ssh-serve' process.

If an environment variable LC_ALL is set, it takes precedence over all other
'LC_xxx' variables, as well as over LANG. So, setting LC_ALL ensures that no
user setting of 'LC_xxx' or 'LANG' could influence ssh-serve badly.

There is one environment variable that might overrule LC_ALL, specifically
for showing messages: 'LANGUAGE'. GNU gettext lets it take precedence over
LC_ALL [1]:
"GNU gettext gives preference to LANGUAGE over LC_ALL and LANG for the
purpose of message handling"

So, also set LANGUAGE to the same value as we set LC_ALL to.

The principle of setting a specific locale in the server process to fix this
error, was first proposed by Dominik Ruf.

[1] https://www.gnu.org/software/gettext/manual/html_node/The-LANGUAGE-variable.html#The-LANGUAGE-variable

=======================
Database schema changes
=======================

Kallithea uses Alembic for :ref:`database migrations <upgrade_db>`
(upgrades and downgrades).

If you are developing a Kallithea feature that requires database schema
changes, you should make a matching Alembic database migration script:

1. :ref:`Create a Kallithea configuration and database <setup>` for testing
   the migration script, or use existing ``development.ini`` setup.

   Ensure that this database is up to date with the latest database
   schema *before* the changes you're currently developing. (Do not
   create the database while your new schema changes are applied.)

2. Create a separate throwaway configuration for iterating on the actual
   database changes::

    kallithea-cli config-create temp.ini

   Edit the file to change database settings. SQLite is typically fine,
   but make sure to change the path to e.g. ``temp.db``, to avoid
   clobbering any existing database file.

3. Make your code changes (including database schema changes in ``db.py``).

4. After every database schema change, recreate the throwaway database
   to test the changes::

    rm temp.db
    kallithea-cli db-create -c temp.ini --repos=/var/repos --user=doe --email doe@example.com --password=123456 --no-public-access --force-yes
    kallithea-cli repo-scan -c temp.ini

5. Once satisfied with the schema changes, auto-generate a draft Alembic
   script using the development database that has *not* been upgraded.
   (The generated script will upgrade the database to match the code.)

   ::

    alembic -c development.ini revision -m "area: add cool feature" --autogenerate

6. Edit the script to clean it up and fix any problems.

   Note that for changes that simply add columns, it may be appropriate
   to not remove them in the downgrade script (and instead do nothing),
   to avoid the loss of data. Unknown columns will simply be ignored by
   Kallithea versions predating your changes.

7. Run ``alembic -c development.ini upgrade head`` to apply changes to
   the (non-throwaway) database, and test the upgrade script. Also test
   downgrades.

   The included ``development.ini`` has full SQL logging enabled. If
   you're using another configuration file, you may want to enable it
   by setting ``level = DEBUG`` in section ``[handler_console_sql]``.

The Alembic migration script should be committed in the same revision as
the database schema (``db.py``) changes.

See the `Alembic documentation`__ for more information, in particular
the tutorial and the section about auto-generating migration scripts.

.. __: http://alembic.zzzcomputing.com/en/latest/


Troubleshooting
---------------

* If ``alembic --autogenerate`` responds "Target database is not up to
  date", you need to either first use Alembic to upgrade the database
  to the most recent version (before your changes), or recreate the
  database from scratch (without your schema changes applied).