This PR was submitted for the 3.3 branch but it was merged into the 2.7 branch instead (closes#7981).Discussion----------Update upload_file.rstIf you edit an existing product with an attached file and do not fill in the fields for the file, after saving the field with the file is resetCommits-------d015048 Update upload_file.rst

* 2.7:  [#8231] fix reStructuredText syntax  Specified import order of config files  [#7981] revert some changes  Update upload_file.rst  Added a missing redirection  Update validation_group_service_resolver.rst  Update redirection_map  Update button_based_validation.rst  Delete group_service_resolver.rst  Create validation_group_service_resolver.rst  [#8290] fix minor typo  Update the setfacl description.  Update associations.rst  Update proxy_examples.rst  Fixed logger processor example

* 2.8: (25 commits)  [#8231] fix reStructuredText syntax  Specified import order of config files  [#7981] revert some changes  Update upload_file.rst  Added a missing redirection  Update validation_group_service_resolver.rst  Update redirection_map  Update button_based_validation.rst  Delete group_service_resolver.rst  Create validation_group_service_resolver.rst  [#8290] fix minor typo  Update the setfacl description.  Update events.rst  Fixed a minor syntax issue  Update phpunit_bridge.rst  First parameter to uniqid must be a stringfix#8321 minor changes in Serializer Component  Update filesystem.rst  Update associations.rst  Update proxy_examples.rst  ...

* 3.3: (40 commits)  [#8273] fix bundle registration code  [#8273] minor rewording  Reworded the built-in web server articles for Symfony 3.3  fix diff code block highlighting  [#8231] fix reStructuredText syntax  Specified import order of config files  [#7981] revert some changes  Update upload_file.rst  Update usage.rst  Update doctrine.rst  Update usage.rst  [#8260] add missing redirection map entry  Delete use_virtuals_forms.rst  Added a missing redirection  Update validation_group_service_resolver.rst  Update redirection_map  Update button_based_validation.rst  Delete group_service_resolver.rst  Create validation_group_service_resolver.rst  [#8290] fix minor typo  ...

* 3.4: (42 commits)  [#8273] fix bundle registration code  [#8273] minor rewording  Reworded the built-in web server articles for Symfony 3.3  fix diff code block highlighting  [#8269] minor rewording  [Console] Commands auto-registration is deprecated  [#8231] fix reStructuredText syntax  Specified import order of config files  [#7981] revert some changes  Update upload_file.rst  Update usage.rst  Update doctrine.rst  Update usage.rst  [#8260] add missing redirection map entry  Delete use_virtuals_forms.rst  Added a missing redirection  Update validation_group_service_resolver.rst  Update redirection_map  Update button_based_validation.rst  Delete group_service_resolver.rst  ...