The EmailMessage documentation describes the initialization parameters
and states they 'can be set at any time prior to calling the send()
method.'. However, the 'headers' parameter's corresponding attribute is
called 'extra_headers'.

Thanks Reza Mohammadi for the report.

``get_template_from_string`` default arguments were breaking
``assertTemplateUsed``. The solution has been to return only the names of the
templates with a ``name`` attribute distinct of ``None``. The default ``name``
kwarg of ``Template`` has been changed to ``None``, more pythonic than ``'<Unknown
Template>'``.

Thanks mitar for the report and Tim Graham for the review.

Refs #14461. Thanks Ramiro Morales for pointing this.

Thanks to Tim for the review.

Add the trimmed option to the blocktrans tag to trim any newlines and
whitespace from its content.

This allows the developer to indent the blocktrans tag without adding
new lines and whitespace to the msgid in the PO file.

Thanks to mpessas for the initial patch and Dmitri Fedortchenko for the
report.

Fixed #13725 -- take url scheme into account in assertRedirects

Thanks to Loic for review.

Scheme is handled correctly when making comparisons between two URLs. If
there isn't any scheme specified in the location where we are redirected to,
the original request's scheme is used. If present, the scheme in
``expected_url`` is the one used to make the comparations to.

 * Safer for use in multiprocess environments
 * Better random culling
 * Cache files use less disk space
 * Safer delete behavior

Also fixed #15806, fixed #15825.

This patch introduces the Prefetch object which allows customizing prefetch
operations.

This enables things like filtering prefetched relations, calling select_related
from a prefetched relation, or prefetching the same relation multiple times
with different querysets.

When a Prefetch instance specifies a to_attr argument, the result is stored
in a list rather than a QuerySet. This has the fortunate consequence of being
significantly faster. The preformance improvement is due to the fact that we
save the costly creation of a QuerySet instance.

Thanks @akaariai for the original patch and @bmispelon and @timgraham
for the reviews.

Instead always create new joins as OUTER.

This commit introduced a new class JoinPromoter that can be used to
abstract away join promotion problems for complex filter conditions.
Query._add_q() and Query.combine() now use the new class.

Also, added a lot of comments about why join promotion is done the way
it is.

Thanks to Tim Graham for original report and testing the changes, and
for Loic Bistuer for review.

Partial forward port of a71ff762 from stable/1.6.x.

deprecated ones.

Thanks to bouke for pointing this out.

Thanks Claude for catching it.

It's possible to use something like {{ foo|dictsort:'bar.baz' }}
but this wasn't tested or documented.

Thanks Tim.

Improved documentation about zh-* deprecation and upgrade path.

Thanks to Baptiste Mispelon for the code reviews.

This issue was fixed when the contenttype restriction was moved from
where clause to the join clause. So, this is tests only addition.