absorb: preserve branch-closing changesets even if empty
This makes the behavior consistent with 'hg commit', which allows to create
otherwise empty changesets if they close the branch. A lost branch closure can
inadvertently re-open a branch, so it should be preserved.
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true