Function doc_merge 

pub fn doc_merge(
    path: &Path,
    value: Value,
    mode: ApplyMode,
    guard: Option<&PathGuard>,
    selector: Option<&str>,
) -> Result<EditResult>

Deep-merge a value into a JSON, YAML, or TOML file.

When selector is None, merges into the document root (single-document files). For multi-document YAML (top-level array of documents), pass Some("0") or Some("[0]") to merge into the first document without replacing the whole stream. Merging a non-array overlay into a multi-doc root returns [crate::exit::TypeErrorError] (peels to crate::fallback::EditErrorKind::TypeError).

Example

use patchloom::api::{self, ApplyMode};
use std::path::Path;

// Root merge (single-doc JSON/YAML/TOML)
let _ = api::doc_merge(
    Path::new("config.json"),
    serde_json::json!({"debug": true}),
    ApplyMode::Apply,
    None,
    None,
)?;

// Multi-doc YAML: merge into document 0 only
let _ = api::doc_merge(
    Path::new("stream.yaml"),
    serde_json::json!({"c": 3}),
    ApplyMode::Apply,
    None,
    Some("0"),
)?;