context: use manifest.find() instead of two separate calls
I noticed this while debugging an extension that's implementing the manifest
interface. Always nice to save a function call.
Differential Revision: https://phab.mercurial-scm.org/D8109
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true