The source control is useful when you implouement custom controls, modules etc, so you make changes to the source /code of your project and you do not inject content which goes to the database. We use data layer which creates custom tables in the database and this is why when you get the latest version of your custom controls this should update the database as well. Adding content to the database is used when you are done with the website and you want to add content to it. Also you could have branches - development, content and production. First you will make all custom development in the "development" branch. Then you will make a merge to the "content" branch and after some tests you should make a merge to the "production". The merge from content to production will require database replication, since you are going to merge content data. The merge from development to content includes only custom logic like custom modules, controls, themes etc.
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