dates: support 'today' and 'yesterday' in parsedate (issue3764)

dates: support 'today' and 'yesterday' in parsedate (issue3764)

Adding support to parsedate in util module to understand the more idiomatic
dates 'today' and 'yesterday'.

Added unified tests and docstring tests for added functionality.

--- a/mercurial/help/dates.txt	Mon Jan 28 12:19:21 2013 -0800
+++ b/mercurial/help/dates.txt	Wed Jan 23 09:51:45 2013 -0800
@@ -18,6 +18,8 @@
 - ``12-6``
 - ``12/6``
 - ``12/6/6`` (Dec 6 2006)
+- ``today`` (midnight)
+- ``yesterday`` (midnight)
 
 Lastly, there is Mercurial's internal format:
 

--- a/mercurial/util.py	Mon Jan 28 12:19:21 2013 -0800
+++ b/mercurial/util.py	Wed Jan 23 09:51:45 2013 -0800
@@ -1027,6 +1027,14 @@
 
     The date may be a "unixtime offset" string or in one of the specified
     formats. If the date already is a (unixtime, offset) tuple, it is returned.
+
+    >>> parsedate(' today ') == parsedate(\
+                                  datetime.date.today().strftime('%b %d'))
+    True
+    >>> parsedate( 'yesterday ') == parsedate((datetime.date.today() -\
+                                               datetime.timedelta(days=1)\
+                                              ).strftime('%b %d'))
+    True
     """
     if not date:
         return 0, 0
@@ -1035,6 +1043,13 @@
     if not formats:
         formats = defaultdateformats
     date = date.strip()
+
+    if date == _('today'):
+        date = datetime.date.today().strftime('%b %d')
+    elif date == _('yesterday'):
+        date = (datetime.date.today() -
+                datetime.timedelta(days=1)).strftime('%b %d')
+
     try:
         when, offset = map(int, date.split(' '))
     except ValueError:

--- a/tests/test-parse-date.t	Mon Jan 28 12:19:21 2013 -0800
+++ b/tests/test-parse-date.t	Wed Jan 23 09:51:45 2013 -0800
@@ -234,3 +234,20 @@
   Sat Apr 15 13:30:00 2006 +0000
   Wed Feb 01 13:00:30 2006 -0500
   Wed Feb 01 13:00:30 2006 +0000
+
+Test issue 3764 (interpreting 'today' and 'yesterday')
+  $ echo "hello" >> a
+  >>> import datetime
+  >>> today = datetime.date.today().strftime("%b %d")
+  >>> yesterday = (datetime.date.today() - datetime.timedelta(days=1)).strftime("%b %d")
+  >>> dates = open('dates', 'w')
+  >>> dates.write(today + '\n')
+  >>> dates.write(yesterday)
+  >>> dates.close()
+  $ hg ci -d "`sed -n '1p' dates`" -m "today is a good day to code"
+  $ hg log -d today --template '{desc}\n'
+  today is a good day to code
+  $ echo "goodbye" >> a
+  $ hg ci -d "`sed -n '2p' dates`" -m "the time traveler's code"
+  $ hg log -d yesterday --template '{desc}\n'
+  the time traveler's code