Use typo3/contrib/vendor/ instead of Packages/
In a result of best practices with composer as well as taking
the tarball distributions (typo3_src.zip) into account, the
directory Packages/ is not necessary right now for either
development and shipping a package.
Distributions (like the composer-installer for TYPO3) can still
use the Packages/ directory in their webroot for other
This means: The TYPO3 source will not contain any
third party library anymore in its GIT repository but instead
these are installed via composer.
For development purposes this means that a "composer install"
command will install all required dev-dependencies into
typo3/contrib/vendor/ which is now ignored by git and no
changes are installed anymore.
For the packaging process a "composer install --no-dev -o" will
be executed when building the tarball and zip files on each
release, downloading the necessary third-party libraries directly
Existing developer installations need to run
"rm -rf typo3/contrib/vendor/ bin Packages/Libraries/ composer.lock"
inside the typo3 repository directory and do a "composer install"
again after applying this patch.