Magento 2 does not allow symlinked files. This is a security feature. However for some development environments (like ours at SwiftOtter)
this can cause issues as we really like keep our files completely separate from Magento (so we don't accidentally mix some core code
into the website repository). This also keeps the
.gitignore to a minimum.
To solve this, Alan Storm posted this article. It, as usual, is an excellent read.
That said, if you want to take this even a step easier, just use this module:
composer require swiftotter/disable-template-validation --dev
php bin/magento module:enable SwiftOtter_DisableTemplateValidation
php bin/magento setup:upgrade
devcomposer area means that it isn't installed on production sites (as I hope you are installing composer there with
--no-dev). Depending on how you get code to production, and if you track all of Magento in your repository, you may have some issues with modules not being found.