Reduce build graph by another eight percent

tool/scripts/explain-deps.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python.com
+
+import os
+import re
+import sys
+
+def GetDeps(path):
+  deps = set()
+  def Dive(path, depth):
+    if path in deps:
+      return
+    deps.add(path)
+    sys.stdout.write('%s%s\n' % ('\t' * depth, path))
+    with open(path) as f:
+      code = f.read()
+    for dep in re.findall(r'[.#]include "([^"]+)"', code):
+      Dive(dep, depth + 1)
+  Dive(path, 0)
+  sys.stdout.write('\n')
+
+for arg in sys.argv[1:]:
+  if os.path.isdir(arg):
+    for dirpath, dirs, files in os.walk(arg):
+      for filepath in files:
+        GetDeps(os.path.join(dirpath, filepath))
+  else:
+    GetDeps(arg)