Add a new filter: strftime. Use the well known function to format a date output. (#23832)

(cherry picked from commit 3f5b304fc2)
rebased for @yannig

docs/docsite/rst/playbooks_filters.rst

@@ -644,6 +644,24 @@ To always exhaust all list use ``zip_longest``::
       debug: msg="{{ [1,2,3]|zip_longest(['a','b','c','d','e','f'], [21, 22, 23], fillvalue='X')|list }}"
 
 
+.. versionadded:: 2.4
+To format a date using a string (like with the shell date command), use the "strftime" filter::
+
+    # Display year-month-day
+    {{ '%Y-%m-%d' | strftime }}
+
+    # Display hour:min:sec
+    {{ '%H:%M:%S' | strftime }}
+
+    # Use ansible_date_time.epoch fact
+    {{ '%Y-%m-%d %H:%M:%S' | strftime(ansible_date_time.epoch) }}
+
+    # Use arbitrary epoch value
+    {{ '%Y-%m-%d' | strftime(0) }}          # => 1970-01-01
+    {{ '%Y-%m-%d' | strftime(1441357287) }} # => 2015-09-04
+
+.. note:: To get all string possibilities, check https://docs.python.org/2/library/time.html#time.strftime
+
 Debugging Filters
 `````````````````
 

lib/ansible/plugins/filter/core.py

@@ -30,13 +30,15 @@ import os.path
 import re
 import string
 import sys
+import time
 import uuid
+import yaml
+
 from collections import MutableMapping, MutableSequence
 from datetime import datetime
 from functools import partial
 from random import Random, SystemRandom, shuffle
 
-import yaml
 from jinja2.filters import environmentfilter, do_groupby as _do_groupby
 
 try:
@@ -121,6 +123,15 @@ def to_datetime(string, format="%Y-%d-%m %H:%M:%S"):
     return datetime.strptime(string, format)
 
 
+def strftime(string_format, second = None):
+    ''' return a date string using string. See https://docs.python.org/2/library/time.html#time.strftime for format '''
+    if second is not None:
+        try:
+            second = int(second)
+        except:
+            raise errors.AnsibleFilterError('Invalid value for epoch value (%s)' % second)
+    return time.strftime(string_format, time.localtime(second))
+
 def quote(a):
     ''' return its argument quoted for shell usage '''
     return shlex_quote(a)
@@ -510,6 +521,9 @@ class FilterModule(object):
             # value as boolean
             'bool': to_bool,
 
+            # date formating
+            'strftime': strftime,
+
             # quote string for shell usage
             'quote': quote,