Add preupload hook to remind people to use AOSP

Add a preupload hook for Telecom to remind people to use AOSP for
Telecom changes.

Test: manual
Change-Id: If2a2cedf95dd14b2fa61ca54762937e586e59aff

PREUPLOAD.cfg

@@ -0,0 +1,2 @@
+[Hook Scripts]
+aosp_hook = ${REPO_ROOT}/packages/services/Telecomm/scripts/aosp_tag_preupload.py ${PREUPLOAD_COMMIT}

scripts/aosp_tag_preupload.py

@@ -0,0 +1,56 @@
+#!/usr/bin/python
+
+import re
+import subprocess
+import sys
+
+# Looks for a string of the form [aosp/branch-name]
+AOSP_BRANCH_REGEX = "\[aosp/[^\]]+\]"
+
+AOSP_COMMIT_TAG_REGEX = "AOSP:"
+AOSP_COMMIT_LINK_REGEX = "aosp/\d+"
+AOSP_INFEASIBLE_REGEX = "Infeasible[ ]?\S+"
+
+ERROR_MESSAGE = """
+The source of truth for this project is AOSP. If you are uploading something to
+a non-AOSP branch first, please provide a link in your commit message to the
+corresponding patch in AOSP. The link should be formatted as follows:
+
+  AOSP: aosp/<patch number>
+
+If it's infeasible for the change to be included in AOSP (for example, if a
+change contains confidential or security-sensitive information), please state
+that it's infeasible and provide reasoning as follows:
+ 
+  AOSP: Infeasible <your reasoning here>
+"""
+
+def main():
+  if _is_in_aosp():
+    sys.exit(0)
+
+  commit_msg = subprocess.check_output(["git", "show",
+                                        sys.argv[1], "--no-notes"])
+  for commit_line in commit_msg.splitlines():
+    if re.search(AOSP_COMMIT_TAG_REGEX, commit_line, re.IGNORECASE):
+      _check_aosp_message(commit_line)
+
+  print(ERROR_MESSAGE)
+  sys.exit(1)
+
+def _is_in_aosp():
+  branch_info = subprocess.check_output(["git", "branch", "-vv"])
+  return re.search(AOSP_BRANCH_REGEX, branch_info) is not None
+
+def _check_aosp_message(aosp_line):
+  if re.search(AOSP_COMMIT_LINK_REGEX, aosp_line):
+    sys.exit(0)
+
+  if re.search(AOSP_INFEASIBLE_REGEX, aosp_line, re.IGNORECASE):
+    sys.exit(0)
+
+  print(ERROR_MESSAGE)
+  sys.exit(1)
+
+if __name__ == '__main__':
+  main()