Why are you putting a project within another project? Each project should be it's own branch set.
NetCoreApi.sln
├── NetCoreApi.csproj
│ ├── project folders and files goes here
├── NetCoreApi.Tests.csproj
│ ├── project folders and files goes here
If you have many projects in a solution, then you can use virtual folders to group "like" projects:
NetCoreApi.sln
├── App
│ ├── projects go here
├── Database
│ ├── projects go here
├── Libraries
│ ├── projects go here
├── Tests
│ ├── projects go here