Fixed #20483.

This can be used to make Django's test suite significantly faster by
reducing the number of models for which content types and permissions
must be created and tables must be flushed in each non-transactional
test.

It's documented for Django contributors and committers but it's branded
as a private API to preserve our freedom to change it in the future.

Most of the credit goes to Anssi. He got the idea and did the research.

Fixed #20483.

This allows using flush on a subset of the tables without having to
manually cascade to all tables with foreign keys to the tables being
truncated, when they're known to be empty.

On databases where truncate is implemented with DELETE FROM, this
doesn't make a difference. The cascade is allowed, not mandatory.

Refs #19875.

Thanks littlepig for the suggestion.

Fixed #20575 -- Typo in docs/topics/forms/media.txt

Fixed typo: froms -> forms

Updated submitting-patches.txt

Few quick fixes to the terminology in order to match what is used on the Django Trac at the moment.

Thanks Roman Alexander for the suggestion.

The docs were ambiguous about the time zone for now(), leading people to
assume that it would be the current time zone rather that UTC.

Thanks margieroginski for the report.

Thanks Timo Graham for noticing the failures.

Fixed #19080 -- Fine-grained control over select_related in admin

The patch for #19385 caused a regression in certain generic relations
.exclude() filters if a subquery was needed. The fix contains a
refactoring to how Query.split_exclude() and Query.trim_start()
interact.

Thanks to Trac alias nferrari for the report.

Thanks Fak3 for the suggestion.

Thanks awsum for the suggestion and Pavel Ponomarev and
Florian Hahn for the patch.

Explicit exception chaining for db exceptions by setting __cause__ in py2

Use __cause__ to expose the underlying database exceptions even
under python 2.

Auth views should be reversed by name, not their locations in
`django.contrib.auth.views`. This allows substituting your own
implementations of the auth views.

Thanks wim@ for the suggestion.

A test failed if the path to the Django checkout contained a dot.

Refs #20485.

Thanks Anssi for reporting this performance bottleneck.

This method is useful to discover files inside apps.

Also regenerated the affected translation template.

Refs #20540.

Thanks d.willy.c.c@ for the suggestion and Melevir and Areski Belaid for work
on the patch.