doctests.test_GitModifier module documentation

Methods tested:
     - L{gbp.git.GitModifier.get_author_env}
     - L{gbp.git.GitModifier.get_committer_env}
     - L{gbp.git.GitModifier.keys}

>>> import gbp.git
>>> modifier = gbp.git.GitModifier('foo', 'bar')
>>> modifier.name
'foo'
>>> modifier.email
'bar'
>>> modifier.get_author_env()['GIT_AUTHOR_EMAIL']
'bar'
>>> modifier.get_author_env()['GIT_AUTHOR_NAME']
'foo'
>>> modifier.get_committer_env()['GIT_COMMITTER_NAME']
'foo'
>>> modifier.get_committer_env()['GIT_COMMITTER_EMAIL']
'bar'
>>> modifier._get_env('foo')
Traceback (most recent call last):
...
gbp.git.modifier.GitModifierError: Neither committer nor author
>>> modifier['name']
'foo'
>>> modifier['email']
'bar'
>>> modifier['date']

Methods tested:
     - L{gbp.git.GitModifier.__init__}

Properties tested:
     - L{gbp.git.GitModifier.date}
     - L{gbp.git.GitModifier.datetime}
     - L{gbp.git.GitModifier.tz_offset}

>>> import gbp.git
>>> import datetime
>>> modifier = gbp.git.GitModifier('foo', 'bar', 1)
>>> modifier.date
'1 +0000'
>>> modifier.date = '1 +0400'
>>> modifier.date
'1 +0400'
>>> modifier['date']
'1 +0400'
>>> modifier.datetime   # doctest: +ELLIPSIS
datetime.datetime(1970, 1, 1, 4, 0, 1, tzinfo=<gbp.git.modifier.GitTz...>)
>>> modifier.date = datetime.datetime(1970, 1, 1, 0, 0, 1)
>>> modifier.date
'1 +0000'
>>> modifier.datetime   # doctest: +ELLIPSIS
datetime.datetime(1970, 1, 1, 0, 0, 1, tzinfo=<gbp.git.modifier.GitTz...>)
>>> modifier.tz_offset
'+0000'

Test C{dict} interface
>>> import gbp.git
>>> modifier = gbp.git.GitModifier('foo', 'bar', 1)
>>> sorted(modifier.keys())
['date', 'email', 'name']
>>> sorted(modifier.items())
[('date', '1 +0000'), ('email', 'bar'), ('name', 'foo')]
>>> modifier.get('name')
'foo'
>>> modifier.get('doesnotexist')