message: Add note about Cargo.lock behavior with [replace]
  The Cargo.lock behavior when using [replace] can be misleading if one
  does not expect multiple versions of the crate to be included. This note
  is intended to assure users that this behavior is expected, and it
  suggests a way to verify their `[replace]` override is preferred.
diff: @@ -216,6 +216,10 @@ repository. While you're waiting for the PR to get merged you can continue to
  work locally with a `[replace]`, and then once the PR is merged and published
  you can remove `[replace]` and use the newly-published version.
  +Note: The `Cargo.lock` file will list two versions of the replaced crate: one
  +for the original crate, and one for the version specified in `[replace]`.
  +`cargo build -v` can verify that only one version is used in the build.
  +
  ### Overriding with local dependencies
  Sometimes you're only temporarily working on a crate and you don't want to have
  