That only works if your application has reasonably few users. Otherwise, your upload will result in some requests hitting a partially completed code base overwrite, that is, only some of your changes have been uploaded at request time, possibly leading to an error. This is a nice strategy for a hobby project, but it plain does not work for a business.
That's not true. For mission-critical apps we route the traffic to the stable version while uploading the new version. This may be similar to what most CI tools do but it doesn't change the fact that we just upload the files and can do it as we see fit. Another good solution is to simply switch off a feature for maintenance while uploading it's files. If your software is well planned, that's a breeze and still keeps the whole process very simple.
Well, you’re shifting the goal posts. The original scenario was simply uploading files to the application folder on production servers and reloading the page.
Of course there are viable strategies to avoid this specific issue, but they all introduce complexity of themselves.
