as described in the symfony cookbook http://symfony.com/doc/current/cookbook/frontend/bower.html

Symfony3 (and some versions of Symfony2) come with a new directory structure.
This updated version of Symfony.gitignore supports this new directory structure
as well as the old one.

The old Symfony.gitignore has been removed (a383e55) as Symfony 1 is no longer
supported.

See e7b7b0f366

Some files don't contain a line separator ('\n') at the end. Add the
missing eol.

In POSIX, all lines of text should end with a newline character by
definition. See
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html
section 3.397 for more.

See https://gist.github.com/jacknagel/1020172 for a gist of the issue.

Symfony 2.0.4 changed standard to using a parameters.yml file, so this change allows for both variants.

Ignore application logs/cache, uploads and published bundle assets.