add a python script to show the runtime packages' dependencies (#725)

* add a python script to show the dependencies

* add the header line and modify the mod

scripts/runtime-dep.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+
+# To run this script, you need to install the 'toml' python package and install the 'graphviz' package:
+# pip install toml
+# sudo apt-get install graphviz
+# the first parameter is the runtime folder
+# python ./scripts/runtime-dep.py ./substrate/runtime | dot -Tpng -o output.png
+import sys
+import os
+import toml
+
+if len(sys.argv) != 2:
+    print("needs the runtime folder.")
+    sys.exit(-1)
+
+runtime_dir = sys.argv[1]
+
+files = [os.path.join(runtime_dir, f, 'Cargo.toml') for f in os.listdir(runtime_dir) if os.path.isfile(os.path.join(runtime_dir, f, 'Cargo.toml')) and f != 'example']
+
+print("digraph G {")
+
+
+PREFIX = "substrate-runtime-"
+
+for f in files:
+    manifest = toml.load(f)
+
+    package_name = manifest['package']['name']
+    deps = [d for d in manifest['dependencies'].keys() if d.startswith(PREFIX)]
+
+    for d in deps:
+        print("    \"{}\" -> \"{}\";".format(package_name, d))
+
+print("}")