Opening previously modified file prompts reload

Hello, I'm having some annoying behavior on the new version of webstorm.

I modify a file and save, then I close the tab and switch git branch using an external tool. When I click on the file again, the changes from git are not taken into account and I get this message "File was changed on disk" and "reload"

When I click on reload, it works.

I would like that if I close a tab, the next time I open the file for it to be automatically reloaded from disk. 
Actually, even if a tab is opened, if I don't have unsaved changes, I would like to have it reloaded from disk on branch switch.

I'm not sure why or how it is keeping a cached version of my file, and how I can disable this.

Thanks