Hi ,
Ideally solution merge we are doing to avoid maintaining multiple solutions. Now as mentioned by David earlier that there may be many scenario.
1. Merge Managed and Unmanaged Solutions.
This scenario comes when you are working on some third party solution or working on top of any existing managed solution. In this scenario I would recommend instead of merging two solution create separate unmanaged solution and include managed solution component there. So always avoid merging concept in this scenario. As per my personal experience I found lot of issue changing on top of managed solution. Here some of them .
- You can not removed managed solution component anymore.
- You can not remove any option set value , attributes ,
- Changing form design and many more.
- Unnecessary component force to keep in the solution.
- Latest version upgrade of managed solution is very difficult.
So I would recommend do not removed any compon
2. Merge Managed Solutions.
Its difficult but you can refer below-
https://msdn.microsoft.com/en-us/library/gg309329.aspx
3. Merge Unmanaged Solutions.
Whenever you are working on any unmanaged solution its basically changing on default solution . So in that case your sitemap and client extension are common so you can easily merge unmanaged solution component into another unmanaged solution , there may be publisher name can be different for the two or more solution component but you can use same publisher name as well.
3.Merging Unmanaged solution using OOB Solution patching [ Must use solution patching]
For Agile methodology when you want to move your solution very frequently . Use solution patching to create patch for your each delivery . Now when you want to plan your latest version of the solution, you usually want to rollup all of the patches that were released for the base solution into the new solution, before you can add new changes in there. This can be done using the “Clone Solution” button. Clone solution means merged all other patches in single solutions.
https://www.inogic.com/blog/2016/01/solution-patching-in-microsoft-dynamics-crm-2016/
https://msdn.microsoft.com/en-in/library/mt593040.aspx
Hope this helps.