Function process_file_includes 

pub fn process_file_includes(
    markdown: &str,
    base_dir: &Path,
    depth: usize,
) -> Result<(String, Vec<IncludedFile>), String>

Process file includes in Nixpkgs/NixOS documentation.

This function processes file include syntax:

```{=include=}
path/to/file1.md
path/to/file2.md
```

Arguments

• markdown - The input markdown text
• base_dir - The base directory for resolving relative file paths
• depth - Current recursion depth (use 0 for initial call)

Returns

Returns Ok((processed_markdown, included_files)) where included_files is a list of all successfully included files.

Errors

Returns Err(message) if recursion depth exceeds [MAX_INCLUDE_DEPTH], which likely indicates a circular include cycle.

Safety

Only relative paths without “..” are allowed for security.