tests/test-check-cargo-lock.t

configitems: add a new config option to control new filenode functionality

This series is adding functionality where we can force create a new filenode for
some files on a merge-commit. This is meant to represent an explicit choice made
by user and hence distingusing the file in the merged commit with the file in
parent by creating a new filenode instead of using the parent one.

This introduces a experimental config option under which this functionality
will be hidden.

A new testcase is added in tests/test-merge-criss-cross.t to test the new
functionality while making the option does not break other scenarios.

Differential Revision: https://phab.mercurial-scm.org/D9026

#require cargo test-repo
  $ . "$TESTDIR/helpers-testrepo.sh"
  $ cd "$TESTDIR"/../rust

Check if Cargo.lock is up-to-date. Will fail with a 101 error code if not.

  $ cargo check --locked --all --quiet

However most CIs will run `cargo build` or similar before running the tests, so we need to check if it was modified

  $ testrepohg diff