Add script for getting milestone contributors (#4396)

* Add script for getting milestone contributors

* Use resp.text instead of resp.content

* Add usage notes

docs/_bin/get-milestone-contributors.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+
+import json
+import sys
+
+import requests
+
+# tested with python 3.6 and requests 2.13.0
+
+if len(sys.argv) != 2:
+  sys.stderr.write('usage: program <milestone-number>\n')
+  sys.stderr.write('Provide the github milestone number, not name. (e.g., 19 instead of 0.10.1)\n')
+  sys.exit(1)
+
+milestone_num = sys.argv[1]
+
+done = False
+page_counter = 1
+contributors = set()
+
+# Get all users who created a closed issue or merged PR for a given milestone
+while not done:
+  resp = requests.get("https://api.github.com/repos/druid-io/druid/issues?milestone=%s&state=closed&page=%s" % (milestone_num, page_counter))
+  pagination_link = resp.headers["Link"]
+
+  # last page doesn't have a "next"
+  if "rel=\"next\"" not in pagination_link:
+    done = True
+  else:
+    page_counter += 1
+
+  issues = json.loads(resp.text)
+  for issue in issues:
+    contributor_name = issue["user"]["login"]
+    contributors.add(contributor_name)
+
+# doesn't work as-is for python2, the contributor names are "unicode" instead of "str" in python2
+contributors = sorted(contributors, key=str.lower)
+for contributor_name in contributors:
+  print("@%s" % contributor_name)