Add master_cleaner tool.

infra_libs/time_functions/parser.py

Index: infra_libs/time_functions/parser.py
diff --git a/infra_libs/time_functions/parser.py b/infra_libs/time_functions/parser.py
new file mode 100644
index 0000000000000000000000000000000000000000..dacc7c335f1b7d82853cefcfcaab19d21053d8cb
--- /dev/null
+++ b/infra_libs/time_functions/parser.py
@@ -0,0 +1,59 @@
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Utility functions to parse time/duration arguments."""
+
+
+import argparse
+import datetime
+import re
+
+
+_TIMEDELTA_CONV = {
+  'us': datetime.timedelta(microseconds=1),
+  'ms': datetime.timedelta(milliseconds=1),
+  's': datetime.timedelta(seconds=1),
+  'm': datetime.timedelta(minutes=1),
+  'h': datetime.timedelta(hours=1),
+  'd': datetime.timedelta(days=1),
+}
+_TIMEDELTA_RE = re.compile(r'(\d+)(\w+)')
+
+
+def parse_timedelta(v):
+  """Returns (datetime.timedelta) The parsed timedelta.
+
+  Args:
+    v (str): The time delta string, a comma-delimited set of <count><unit>
+        tokens comprising the timedelta (e.g., 10d,2h is 10 days, 2 hours).
+
+  Raises:
+    ValueError: If parsing failed.
+  """
+  result = datetime.timedelta()
+  for comp in v.split(','):
+    match = _TIMEDELTA_RE.match(comp)
+    if match is None:
+      raise ValueError('Invalid timedelta token (%s)' % (comp,))
+    count, unit = int(match.group(1)), match.group(2)
+    unit_value = _TIMEDELTA_CONV.get(unit)
+    if unit_value is None:
+      raise ValueError('Invalid timedelta token unit (%s)' % (unit,))
+    result += (unit_value * count)
+  return result
+
+
+def argparse_timedelta_type(v):
+  """Returns (datetime.timedelta) The parsed timedelta.
+
+  This is an argparse-compatible version of `parse_timedelta` that raises an
+  argparse.ArgumentTypeError on failure instead of a ValueError.
+
+  Raises:
+    argparse.ArgumentTypeError: If parsing failed.
+  """
+  try:
+    return parse_timedelta(v)
+  except ValueError as e:
+    raise argparse.ArgumentTypeError(e.message)