From 2a23592c21dafc1ece673700db077fcd61e06200 Mon Sep 17 00:00:00 2001
From: Josh Duff <josh.duff@equipmentshare.com>
Date: Mon, 21 Oct 2019 09:59:57 -0500
Subject: [PATCH] Revert "Manually rolling back #167"

This reverts commit 55067352a92c65a6c44a5165f3387720aae1e192.
---
 index.js      | 12 ++++++------
 test/merge.js |  9 +++++++++
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/index.js b/index.js
index f0baf14..e3135d2 100644
--- a/index.js
+++ b/index.js
@@ -54,12 +54,12 @@ function mergeObject(target, source, options) {
 }
 
 function deepmerge(target, source, options) {
-	options = options || {}
-	options.arrayMerge = options.arrayMerge || defaultArrayMerge
-	options.isMergeableObject = options.isMergeableObject || defaultIsMergeableObject
-	// cloneUnlessOtherwiseSpecified is added to `options` so that custom arrayMerge()
-	// implementations can use it. The caller may not replace it.
-	options.cloneUnlessOtherwiseSpecified = cloneUnlessOtherwiseSpecified
+	options = Object.assign({
+		arrayMerge: defaultArrayMerge,
+		isMergeableObject: defaultIsMergeableObject
+	}, options, {
+		cloneUnlessOtherwiseSpecified: cloneUnlessOtherwiseSpecified
+	})
 
 	var sourceIsArray = Array.isArray(source)
 	var targetIsArray = Array.isArray(target)
diff --git a/test/merge.js b/test/merge.js
index 44eca9f..f243422 100644
--- a/test/merge.js
+++ b/test/merge.js
@@ -637,3 +637,12 @@ test('copy symbol keys in target that do exist on the target', function(t) {
 	t.equal(res[mySymbol], 'value1')
 	t.end()
 })
+
+test('should not mutate options', function(t) {
+	var options = {};
+
+	merge({}, {}, options);
+
+	t.deepEqual(options, {});
+	t.end();
+})