Add a function to embedded_migrations! to check if migration is needed

[kpcyrd]

It seems right now two functions are exported in the module that is generated by embedded_migrations!:

• run
• run_with_output

I would like to have a 3rd function, along the lines of fn migrations_needed() -> bool, that can be used to check if migrations are available/needed.

The idea is that this function can be used to determine if embedded_migrations::run needs to be executed and also to inform the user that migrations are going to be executed:

if embedded_migrations::migrations_needed() {
    println!("executing migrations);
    embedded_migrations::run(&db)?;
}

[sgrif]

Thank you for the feature request. We're currently in the process of a cleanup of the issue tracker, and aren't currently accepting feature requests (there will be an official policy written soon, but the TL;DR is that open issues should reflect something that is a bug or on our immediate roadmap).

We're happy to discuss feature requests, but the place to do so is discourse.diesel.rs, not the issue tracker.