From e8e79ce77dc92dca9fb6c43b01c3b1116de963b6 Mon Sep 17 00:00:00 2001
From: Ivan Kuchin <tadump+git@gmail.com>
Date: Wed, 26 Apr 2023 00:27:19 +0200
Subject: [PATCH 1/3] add basic diff test

---
 test/commit_test.rb | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/test/commit_test.rb b/test/commit_test.rb
index 12f20aba0..404267628 100644
--- a/test/commit_test.rb
+++ b/test/commit_test.rb
@@ -362,6 +362,21 @@ def test_commit_summary
     commit = Rugged::Commit.lookup(@repo, commit_id)
     assert_equal "This is the commit message", commit.summary
   end
+
+  def test_diff
+    oid = "5b5b025afb0b4c913b4c338a42934a3863bf3644"
+    obj = @repo.lookup(oid)
+
+    assert_equal <<-PATCH, obj.diff.patch
+diff --git b/new.txt a/new.txt
+new file mode 100644
+index 0000000..fa49b07
+--- /dev/null
++++ a/new.txt
+@@ -0,0 +1 @@
++new file
+    PATCH
+  end
 end
 
 class CommitWriteTest < Rugged::TestCase

From ac3251d5343fd86a1547ed4f813e206b52b1912a Mon Sep 17 00:00:00 2001
From: Ivan Kuchin <tadump+git@gmail.com>
Date: Wed, 26 Apr 2023 00:28:24 +0200
Subject: [PATCH 2/3] test options as hash passed to commit#diff is not changed

---
 test/commit_test.rb | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/test/commit_test.rb b/test/commit_test.rb
index 404267628..720bcc6cf 100644
--- a/test/commit_test.rb
+++ b/test/commit_test.rb
@@ -377,6 +377,15 @@ def test_diff
 +new file
     PATCH
   end
+
+  def test_diff_options_not_changing
+    oid = "5b5b025afb0b4c913b4c338a42934a3863bf3644"
+    obj = @repo.lookup(oid)
+
+    options = {}
+
+    assert_equal obj.diff(options).patch, obj.diff(options).patch
+  end
 end
 
 class CommitWriteTest < Rugged::TestCase

From 92c7d58209b3ea1a1f48504482651ec2602d1398 Mon Sep 17 00:00:00 2001
From: Ivan Kuchin <tadump+git@gmail.com>
Date: Wed, 26 Apr 2023 00:28:41 +0200
Subject: [PATCH 3/3] don't change options hash passed to commit#diff

---
 lib/rugged/commit.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/rugged/commit.rb b/lib/rugged/commit.rb
index 81db6813a..4c8da1ab7 100644
--- a/lib/rugged/commit.rb
+++ b/lib/rugged/commit.rb
@@ -34,7 +34,7 @@ def diff(*args)
       # then diff against the prior commit
       if args.empty? || args.first.is_a?(Hash)
         other = parents.first
-        opts[:reverse] = !opts[:reverse]
+        opts = opts.merge(:reverse => !opts[:reverse])
       end
       self.tree.diff(other, opts)
     end