Function drift_report 

pub fn drift_report(
    manifest_path: &Path,
    dialect: &str,
    url: &str,
) -> Result<usize, String>

Reports drift between the manifest at manifest_path and the database url names, and answers how many differences there were.

The count is the point: a command that only printed would be a command no test could tell the two answers apart with, and no CI job could act on. The caller turns a non-zero count into a non-zero exit.

Errors

A message for the operator when the manifest cannot be read, the dialect is unsupported, the database cannot be reached, or its catalog cannot be read.