rust-tests: add test to check if `Cargo.lock` is up-to-date...
rust-tests: add test to check if `Cargo.lock` is up-to-date
An out-of-date `Cargo.lock` is the source of rebase conflicts, prevents a
reproductible build, introduces desync between the series that introduces a
change in dependencies and the one that eventually commits the `Cargo.lock`,
and is just a general annoyance.
This commit demonstrates that the test works, the next one fixes the
currently out-of-date `Cargo.lock`.
Differential Revision:
https://phab.mercurial-scm.org/D9079
