ccls not detecting some header files

[ItsLiyua]

I have a project that looks like this

project-root:
  .git
  src
  inc
  my-library
    .git
    src
    inc
  CMakeLists.txt

The problem is, that when I try to edit a source file in the submodule it does not detect other headers from the submodule. In The parent directory everything works fine. When I rename .git to git it works fine too which leads me to believe, that the submodule has its own project root. The fact that it gets its own .ccls-cache directory also suggests that.

Since it isn't supposed to be compiled by itself it doesn't have a CMakeLists.txt file and I can't really create a compile_commands.json file.

Creating a .ccls-root in my parent project did not help.

How would I fix this so that the child project does not become its own ccls indexing space?

Thanks for your help!