Super simple trait that patterns the value "updae" and "get".

The author of this crate is not good at English.
Forgive me if the document is hard to read.

The Upget trait only has an upget method, which just updates self value with a closure and then retrieves it. That's all there is to it, but it allows you to refactor common code patterns.

For example, the following code can be refactored...

fn clone_with_sort(vec: &Vec<String>) -> Vec<String> {
    let mut result = vec.clone();
    result.sort();
    result
}

as follows.

fn clone_with_sort(vec: &Vec<String>) -> Vec<String> {
    vec.clone().upget(|x| x.sort())
}

Such refactoring has the following benefits.

• Simplification of code.
• Elimination of intermediate variables.
• Elimination of the mut specification.

See CHANGELOG.