In cases where you want to integrate libraries that reside in the project structure (for example as submodules and/or plain in-tree outside of the sub-tree for your app) you can use the @file:// specifier which allows you to specify paths relative to the project root (folder in which .tipi/ resides)

Given the following project structure:

project/
├── app/
│   ├── .tipi/
│   │   └── deps
│   └── my_app.cpp
└── vendors/
    ├── termcolor/(...)
    └── nlohmann_json/(...)

Add the following entries to /project/app/.tipi/deps to add ikalnytskyi/termcolor and nlohmann/json to your app

{
  "file://../vendors/termcolor": {},
  "file://../vendors/nlohmann_json": {}
}

The full detail about the syntax and options of the deps file can be found in the documentation.

Note:

If the example project had the dependencies living in a vendors folder inside the /project/app folder instead, no configuration would be required.

Another alternative would have been to start the source scan at the the /project level