Bump to v4.17.3.

_customDefaultsMerge.js

@@ -0,0 +1,31 @@
+define(['./_baseMerge', './isObject'], function(baseMerge, isObject) {
+
+  /** Used as a safe reference for `undefined` in pre-ES5 environments. */
+  var undefined;
+
+  /**
+   * Used by `_.defaultsDeep` to customize its `_.merge` use to merge source
+   * objects into destination objects that are passed thru.
+   *
+   * @private
+   * @param {*} objValue The destination value.
+   * @param {*} srcValue The source value.
+   * @param {string} key The key of the property to merge.
+   * @param {Object} object The parent object of `objValue`.
+   * @param {Object} source The parent object of `srcValue`.
+   * @param {Object} [stack] Tracks traversed source values and their merged
+   *  counterparts.
+   * @returns {*} Returns the value to assign.
+   */
+  function customDefaultsMerge(objValue, srcValue, key, object, source, stack) {
+    if (isObject(objValue) && isObject(srcValue)) {
+      // Recursively merge objects and arrays (susceptible to call stack limits).
+      stack.set(srcValue, objValue);
+      baseMerge(objValue, srcValue, undefined, customDefaultsMerge, stack);
+      stack['delete'](srcValue);
+    }
+    return objValue;
+  }
+
+  return customDefaultsMerge;
+});