Function apply_reparent

atomic-core/src/crdt/apply/branch.rs:371–392

Applies a Reparent operation to change a branch's chain position without touching its state or content. # Behavior 1. Verifies the branch exists. 2. Calls `update_branch_after` to rewrite the BRANCH_AFTER row. The walker reads BRANCH_AFTER directly, so this is the entire effect. # Errors - `BranchNotFound` - The branch doesn't exist.

(
    txn: &mut T,
    context: &mut ApplyContext,
    branch_id: BranchId,
    new_after: Option<BranchId>,
)

///
/// - `BranchNotFound` - The branch doesn't exist.
fn apply_reparent<T: MutCrdtTxnT>(
    txn: &mut T,
    context: &mut ApplyContext,
    branch_id: BranchId,
    new_after: Option<BranchId>,
) -> ApplyResult<()> {
    // Verify branch exists
    if !txn
        .has_branch(branch_id)
        .map_err(|e| storage_err(e, "checking branch exists"))?
    {
        return Err(ApplyError::branch_not_found(branch_id));
    }

    txn.update_branch_after(branch_id, new_after)
        .map_err(|e| storage_err(e, "updating branch after-ref"))?;

    // No dedicated counter on ApplyContext for reparent yet — track as a
    // skipped op for accounting until we add `record_branch_reparented`.
    context.record_skipped();
    Ok(())
}

// Validation Helpers