docs: Add dependency management

docs/contributing/contributing.rst

@@ -18,3 +18,4 @@ Welcome to the contribution guides and development docs of RhodeCode.
    db-schema
    dev-settings
    api
+   dependencies

docs/contributing/dependencies.rst

@@ -0,0 +1,60 @@
+
+=======================
+ Dependency management
+=======================
+
+
+Overview
+========
+
+We use the Nix package manager to handle our dependencies. In general we use the
+packages out of the package collection `nixpkgs`. For frequently changing
+dependencies for Python and JavaScript we use the tools which are described in
+this section to generate the needed Nix derivations.
+
+
+Python dependencies
+===================
+
+We use the tool `pip2nix` to generate the Nix derivations for our Python
+dependencies.
+
+Generating the dependencies should be done with the following command:
+
+.. code:: shell
+
+   pip2nix generate --license
+
+
+.. note::
+
+   License extraction support is still experimental, use the version from the
+   following pull request: https://github.com/ktosiek/pip2nix/pull/30
+
+
+
+Node dependencies
+=================
+
+After adding new dependencies via ``npm install --save``, use `node2nix` to
+update the corresponding Nix derivations:
+
+.. code:: shell
+
+   cd pkgs
+   node2nix --input ../package.json \
+            -o node-packages.nix \
+            -e node-env.nix \
+            -c node-default.nix \
+            -d --flatten
+
+
+Bower dependencies
+==================
+
+Frontend dependencies are managed based on `bower`, with `bower2nix` a tool
+exists which can generate the needed Nix derivations:
+
+.. code:: shell
+
+   bower2nix bower.json pkgs/bower-packages.nix