rust/Cargo.toml

mergestate: move staticmethod _filectxorabsent to module level

I suspect this was a static method just because it made merge.py feel
less messy, but now we have a mergestate package so we can do better.

Differential Revision: https://phab.mercurial-scm.org/D8591

[workspace]
members = ["hg-core", "hg-cpython"]
exclude = ["chg", "hgcli"]