hg: make `clean` return consistent with the `update` function
The function return a boolean and is used as such. Lets be explicit about it.
Differential Revision: https://phab.mercurial-scm.org/D10156
[fix]
clang-format:command = clang-format --style file
clang-format:pattern = set:(**.c or **.cc or **.h) and not "include:contrib/clang-format-ignorelist"
rustfmt:command = rustfmt +nightly
rustfmt:pattern = set:"**.rs" - "mercurial/thirdparty/**"
black:command = black --config=black.toml -
black:pattern = set:**.py - mercurial/thirdparty/**
# Mercurial doesn't have any Go code, but if we did this is how we
# would configure `hg fix` for Go:
go:command = gofmt
go:pattern = set:**.go