Add contributing docs

CONTRIBUTING.md

@@ -0,0 +1,55 @@
+Contributing
+============
+
+Contributions are welcome, and they are greatly appreciated! Every
+little bit helps.
+
+You can contribute in many ways:
+
+Types of Contributions
+----------------------
+
+### Report Bugs
+
+Report bugs at <https://github.com/hpyproject/hpy/issues>.
+
+When reporting a bug, please include:
+
+- Your operating system name and version.
+- Any details about your local setup that might be helpful in
+    troubleshooting.
+- Detailed steps to reproduce the bug.
+
+### Donate to HPy
+
+Become a financial contributor and help us sustain the HPy community: [Contribute to HPy](https://opencollective.com/hpy/contribute).
+
+### Fix Bugs or Implement Features
+
+Look through the GitHub issues for bugs or proposals being discussed
+or ready for implementation.
+
+### Write Documentation
+
+HPy could always use more documentation, whether as part of the
+official HPy docs, in docstrings, or even on the web in blog
+posts, articles, and such.
+
+Get Started!
+------------
+
+You can test your environment by running 
+
+```bash
+proof-of-concept/test_pof.sh wheel universal
+```
+
+This should build HPy and a proof of concept (demo) extension and
+then run a pytest that validates both.
+
+Until we get around to more comprehensive documentation, you
+can reverse engineer how the system works by looking at these
+files:
+
+- `proof-of-concept/test_pof.sh`
+- `proof-of-concept/setup.py`

proof-of-concept/test_pof.sh

@@ -105,6 +105,24 @@ setup_py_install() {
 
 # ======== main code =======
 
+# validate arguments
+if [[ "$#" -lt 1  || ( "$#" -lt 2  && "$1" != "clean") ]]; then
+  echo "Usage: $0 COMMAND [TARGET_ABI]" >&2
+  echo "Commands:" >&2
+  echo "  wheel TARGET_ABI: build a wheel, install and test"
+  echo "  setup_py_install TARGET_ABI: install poc using 'setup.py install' & run tests" >&2
+  echo "  clean: clean build artifacts" >&2
+  echo "Target ABIs:" >&2
+  echo "  universal: Binary intended for any Python implementation" >&2
+  echo "  cpython : Binary optimized for CPython" >&2
+  exit 1
+fi
+
+if [ ! -d "proof-of-concept" ] ; then
+    echo "Script must be run in the repo root" >&2
+    exit 1
+fi
+
 # call the function mentioned as the first arg
 COMMAND="$1"
 shift