write patches via gitremote push trigger (#79)

* write patches via gitremote push trigger

* implement context variables intead of custom database class

docs/ahriman.models.rst

@@ -36,6 +36,14 @@ ahriman.models.build\_status module
    :no-undoc-members:
    :show-inheritance:
 
+ahriman.models.context\_key module
+----------------------------------
+
+.. automodule:: ahriman.models.context_key
+   :members:
+   :no-undoc-members:
+   :show-inheritance:
+
 ahriman.models.counters module
 ------------------------------
 

docs/architecture.rst

@@ -169,6 +169,15 @@ Utils
 
 For every external command run (which is actually not recommended if possible) custom wrapper for ``subprocess`` is used. Additional functions ``ahriman.core.auth.helpers`` provide safe calls for ``aiohttp_security`` methods and are required to make this dependency optional.
 
+Context variables
+^^^^^^^^^^^^^^^^^
+
+Package provides implicit global variables which can be accessed from ``ahriman.core`` package as ``context`` variable, wrapped by ``contextvars.ContextVar`` class. The value of the variable is defaulting to private ``_Context`` class which is defined in the same module. The default values - such as ``database`` and ``sign`` - are being set on the service initialization.
+
+The ``_Context`` class itself mimics default collection interface (as is Mapping) and can be modified by ``_Context.set`` method. The stored variables can be achieved by ``_Context.get`` method, which is unlike default ``Mapping`` interface also performs type and presence checks.
+
+In order to provide statically typed interface, the ``ahriman.models.context_key.ContextKey`` class is used for both ``_Content.get`` and ``_Content.set`` methods; the context instance itself, however, does not store information about types.
+
 Submodules
 ^^^^^^^^^^
 

docs/triggers.rst

@@ -36,6 +36,40 @@ Trigger which can be used for reporting. It implements ``on_result`` method and
 
 This trigger takes build result (``on_result``) and performs syncing of the local packages to the remote mirror (e.g. S3 or just by rsync).
 
+Context variables
+-----------------
+
+By default, only configuration and architecture are passed to triggers. However, some triggers might want to have access to other high-level wrappers. In order to provide such ability and avoid (double) initialization, the service provides a global context variables, which can be accessed from ``ahriman.core`` package:
+
+.. code-block:: python
+
+   from ahriman.core import context
+
+   ctx = context.get()
+
+Just because context is wrapped inside ``contexvars.ContextVar``, you need to explicitly extract variable by ``get()`` method. Later you can extract any variable if it is set, e.g.:
+
+.. code-block:: python
+
+   from ahriman.core.database import SQLite
+   from ahriman.models.context_key import ContextKey
+
+   database = ctx.get(ContextKey("database", SQLite))
+
+In order to provide typed API, all variables are stored together with their type. The ``get(ContextKey)`` method will throw ``KeyError`` in case if key is missing. Alternatively you can set your own variable inside context:
+
+.. code-block:: python
+
+   ctx.set(ContextKey("answer", int), 42)
+   context.set(ctx)
+
+Note, however, that there are several limitations:
+
+* Context variables are immutable, thus you cannot override value if the key already presented.
+* The ``return_type`` of ``ContextKey`` should match the value type, otherwise exception will be thrown.
+
+The ``context`` also implements collection methods such as ``__iter__`` and ``__len__``.
+
 Trigger example
 ---------------