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.

mercurial/help/dates.txt

@@ -18,6 +18,8 b' Many date formats are valid. Here are so'
 - ``12-6``
 - ``12/6``
 - ``12/6/6`` (Dec 6 2006)
+- ``today`` (midnight)
+- ``yesterday`` (midnight)
 
 Lastly, there is Mercurial's internal format:
 

mercurial/util.py

@@ -1027,6 +1027,14 b' def parsedate(date, formats=None, bias={'
 
     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 b' def parsedate(date, formats=None, bias={'
     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:

tests/test-parse-date.t

@@ -234,3 +234,20 b" Test date formats with '>' or '<' accomp"
   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