Rebase finishes incorrectly with rugged later than v0.25.0b2

Rugged::Rebase#finish doesn't get back a current branch to the original.

What am I doing wrong?

How to reproduce

57b46eb (Today's HEAD): ❌

$ git clone https://github.com/libgit2/rugged.git
$ cd rugged
4 git submodule update --init
$ rake compile:rugged

$ git checkout -b test
Switched to a new branch 'test'

$ ruby -I lib test.rb
$ git status
HEAD detached at refs/heads/test  # <-- NG
...

2998346 ❌

$ git checkout 2998346
$ git submodule update; rake clean; rake compile:rugged
$ git branch -D test; git co -b test
Deleted branch test (was 57b46eb).
Switched to a new branch 'test'

$ ruby -I lib test.rb
$ git status
HEAD detached from refs/heads/test  # <-- NG
...

2139edd ⭕

$ git checkout 2139edd
$ git submodule update; rake clean; rake compile:rugged
$ git branch -D test; git co -b test
Deleted branch test (was 2998346).
Switched to a new branch 'test'

$ ruby -I lib test.rb
$ git status
HEAD detached test  # <-- OK
...

ruby code

# test.ruby

require 'rugged'

repo = Rugged::Repository.new('.')
r = Rugged::Rebase.new(repo, "refs/heads/test", "refs/heads/master")

r.finish({name: 'me', email: 'me@example.com'})

Start at the Rugged::Rebase#finish entry point and run the supplied test.rb reproduction against the listed revisions. Compare the resulting branch state from git status with the expected attached test branch, then trace the rebase finish behavior until the current branch is restored correctly.