Hi,
a branch is shown incorrectly when contains utf-8 characters

Branch name:
refs/heads/zażółć_gęślą_jaźń

The issue can be fixed by adding encoding in SymbolicReference._get_ref_info_helper.
Proposed change:
Replace

with open(osp.join(repodir, ref_path), 'rt') as fp:

Current result (e.g. shown as active_branch):
refs/heads/zaÅ1⁄4Ã3łć_gÄTMÅ›lÄ..._jaÅoÅ„

with

with open(osp.join(repodir, ref_path), 'rt', encoding="utf-8") as fp:

Expected result:
refs/heads/zażółć_gęślą_jaźń