files: extract code for extra filtering of the `removed` entry into copies
We want to reduce the set of `removed` files that to the set of files actually
removed. That `removed` set is used as of the changeset centric algorithm,
having smaller sets means less processing and faster computation.
In this changeset we extract the code to be a function of it own. We will make
use of it in the next changesets.
Differential Revision: https://phab.mercurial-scm.org/D8588
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true