Merge branch 'stubgen-docs' into 'master'

document stubgen functionality in readme

See merge request !73

README.md

@@ -92,6 +92,29 @@ shell command:
 $ python -m cmmnbuild_dep_manager resolve
 ```
 
+### Stub generation
+
+The extra package `cmmnbuild_dep_manager[stubgen]` provides support for generating python type stubs (`pyi` files per PEP-484) from Java packages using [stubgenj].
+
+Python packages registered in `cmmnbuild_dep_manager` can set the variable `__stubgen_packages__` in their `__init__.py` file. The value must contain a list of java packages to generate stubs for, as strings. Any sub-packages are automatically included, e.g.
+```python
+__stubgen_packages__ = [
+    "java",
+    "cern.lsa",
+    "cern.accsoft.commons"
+]
+```
+would instruct `cmmnbuild_dep_manager` to generate stubs for the Java packages `java`, `cern.lsa` and `cern.accsoft.commons`, including all of their sub-packages.
+
+The actual stub (re-)generation is triggered via the command line interface:
+```bash
+$ python -m cmmnbuild_dep_manager stubgen
+```
+
+By default stubs are placed where `cmmnbuild_dep_manager` is installed (e.g. in the active venv).
+
+[stubgenj]: https://gitlab.cern.ch/scripting-tools/stubgenj
+
 ### Jar inspection helper functions
 
 Helper functions are provided to inspect the classes in the downloaded jars.