AssetDatabase.ExportPackage

Description

Exports the assets identified by assetPathNames to a unitypackage file in fileName.

Additional resources: ExportPackageOptions for information on how you can affect what gets exported.

using System.Collections.Generic;
using UnityEditor;
using UnityEngine;

public class AssetDatabaseExamples : MonoBehaviour
{
    [MenuItem("AssetDatabase/Export")]
    static void Export()
    {
        var exportedPackageAssetList = new List<string>();
        //Find all shaders that have "Surface" in their names and add them to the list
        foreach (var guid in AssetDatabase.FindAssets("t:Shader Surface", new []{"Assets/Shaders"}))
        {
            var path = AssetDatabase.GUIDToAssetPath(guid);
            exportedPackageAssetList.Add(path);
        }

        //Add Prefabs folder into the asset list
        exportedPackageAssetList.Add("Assets/Prefabs");
        //Export Shaders and Prefabs with their dependencies into a .unitypackage
        AssetDatabase.ExportPackage(exportedPackageAssetList.ToArray(), "ShadersAndPrefabsWithDependencies.unitypackage",
            ExportPackageOptions.Recurse | ExportPackageOptions.IncludeDependencies);
    }
}