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Thomas De Schampheleire

cli: add command 'kallithea-cli front-end-build'

Kallithea is under the GPL license, and we can thus only distribute any
generated code if we also ship the corresponding source.

We are moving towards a web front-end that use npm to download and compile
various open source components. The components might not be GPL, but if we
distribute any parts of their code (compiled or converted to other
representation), then we also must distribute the corresponding source under
the GPL.

It doesn't seem feasible for us to distribute the source of everything that
npm downloads and includes when we are building. It thus also doesn't seem
feasible for us to build and ship the compiled (possibly minified) front-end
code. Instead, we have to make it as smooth as possible for our users to
get up and running.

It doesn't seem feasible for us to ship or install npm. We must assume it is
available. That requirement must be documented clearly, and we must recommend
how to install npm for the most common platforms.

We could perhaps just document what manual steps to run. Kallithea doesn't
work out of the box anyway - it has to be configured and initialized. Extra
steps might not be a big problem.

Another approach is to call out to npm while pip is installing Kallithea and
download the requirements and build the files. It can be done by customizing
setuptools commands in setup.py. But: Python packaging is fragile. Even
though we only support pip, it really isn't built for things like this.
Custom output is muted and buffered and only shown if running with -v or the
command fails. And pip and setup.py can be used to build and install in so
many ways that we probably can't make it work reliably with all ways of
installing Kallithea.

The approach implemented by this commit is to add a custom cli command
'front-end-build' to run the required commands. This single user-facing
command can internally run various steps as needed. The only current
requirement is the presence of npm and an internet connection.

For now, this will just create/update style.css ... but currently probably
without any actual changes. The files created by npm (and the node_modules
directory) must *not* be a part of the release package made with 'setup.py
sdist'.

(Commit message is mostly written by Mads Kiilerich)

=======================
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).