Cannot detach head

[hramrach]

code

import tempfile
import pygit2
import subprocess
import shutil
import sys

print(f"python: {sys.version}")
print(f"libgit2: {pygit2.LIBGIT2_VERSION}")
print(f"pygit2: {pygit2.__version__}")

repodir = tempfile.mkdtemp()
repo = pygit2.init_repository(repodir, bare=True)

sig = pygit2.Signature('Test User', 'testuser@nowhere.net')

data = 'blah blah master'
tree = repo.TreeBuilder()
tree.insert('file', repo.create_blob(data.encode()), pygit2.GIT_FILEMODE_BLOB)

master_commit_oid = repo.create_commit('HEAD', sig, sig, 'master commit', tree.write(), [])

repo.lookup_branch('master').set_target(master_commit_oid)

print(f"dullahan: {repo.head_is_detached}")

repo.head.set_target(master_commit_oid) # no effect?

print(f"dullahan: {repo.head_is_detached}")

subprocess.run(['cat', repodir + '/HEAD'])

data = 'blah blah feature'
tree = repo.TreeBuilder()
tree.insert('file', repo.create_blob(data.encode()), pygit2.GIT_FILEMODE_BLOB)

feature_commit_oid = repo.create_commit('HEAD', sig, sig, 'feature commit', tree.write(), [master_commit_oid])

feature_commit = repo.resolve_refish(feature_commit_oid.hex)[0] # why is this needed?!

repo.branches.local.create('feature', feature_commit)

subprocess.run(['git', '--no-pager', '--git-dir', repodir, 'log'])
shutil.rmtree(repodir)

output

python: 3.11.8 (main, Feb 29 2024, 12:19:47) [GCC]
libgit2: 1.8.0
pygit2: 1.14.1
dullahan: False
dullahan: False
ref: refs/heads/master
commit fd24ce9e6e104d9a3379bd533d1fc77c7ed4c171 (HEAD -> master, feature)
Author: Test User <testuser@nowhere.net>
Date:   Mon Apr 29 18:56:30 2024 +0200

    feature commit

commit f46e8132e419552a55edaceda91346b9ebdf2a45
Author: Test User <testuser@nowhere.net>
Date:   Mon Apr 29 18:56:30 2024 +0200

    master commit