#7220)

* ensure content files are available in config

If you use the cli with the `--content` option, then we first resolve
the config (empty), then add the `content` to the config. The issue is
that this means that the content will be empty when you resolve it
initially. This results in a warning in your terminal.

Now, we will make sure to merge 2 configs if you have the `--content`
data passed. We will also make sure to override the final
`config.content.files` to whatever you passed in to make sure that this
is the same behaviour as before.

* update changelog