revlogv2: don't assume that the sidedata of the last rev is right after data
We are going to be rewriting sidedata soon, it's going to be appended to the
revlog data file, meaning that the data and the sidedata might not be
contiguous.
Differential Revision: https://phab.mercurial-scm.org/D10025
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true