Package demo scripts and data in sdists and wheels

This enables users who haven't cloned the git repository to still run
the demos.

A few unnecessary entries were removed from MANIFEST.in too. TODO: see
whether we can get rid of MANIFEST.in completely and use setuptools'
find_packages and package_data instead.

MANIFEST.in

@@ -1,6 +1,3 @@
-include README.md CHANGELOG.md LICENSE.txt CITE.md AUTHORS.md MANIFEST.in setup.py requirements.txt .gitignore
+include CHANGELOG.md CITE.md AUTHORS.md
 include cherab/core/VERSION
-recursive-include cherab *.py *.pyx *.pxd *.json *.cl *.npy *.obj
-prune demos*
-
-
+recursive-include cherab *.pyx *.pxd *.json *.cl *.npy *.obj

setup.py

@@ -1,8 +1,10 @@
 from setuptools import setup, find_packages, Extension
+from collections import defaultdict
 import sys
 import numpy
 import os
 import os.path as path
+from pathlib import Path
 import multiprocessing
 from Cython.Build import cythonize
 
@@ -68,6 +70,16 @@
     compiler_directives=cython_directives,
 )
 
+# Include demos in a separate directory in the distribution as data_files.
+demo_parent_path = Path("share/cherab/demos/core")
+data_files = defaultdict(list)
+demos_source = Path("demos")
+for item in demos_source.rglob("*"):
+    if item.is_file():
+        install_dir = demo_parent_path / item.parent.relative_to(demos_source)
+        data_files[str(install_dir)].append(str(item))
+data_files = list(data_files.items())
+
 # parse the package version number
 with open(path.join(path.dirname(__file__), "cherab/core/VERSION")) as version_file:
     version = version_file.read().strip()
@@ -105,8 +117,9 @@
         "matplotlib",
         "raysect==0.8.1",
     ],
-    packages=find_packages(),
+    packages=find_packages(include=["cherab*"]),
     include_package_data=True,
+    data_files=data_files,
     zip_safe=False,
     ext_modules=extensions,
 )