分层日志记录器

对 log crate 的简单包装，允许在运行时为将来的调试宏调用添加任意信息。

背后的魔法是一个 thread_local RefCell<Vec<String>>，当填充时将包含包含的标识符，用 ": " 分隔。

#[macro_use] extern crate log;
#[macro_use] extern crate scoped_log;
extern crate env_logger;

fn main () {
    let _ = env_logger::init();

    scoped_info!("1");
    {
        push_log_scope!("outer-scope");
        scoped_info!("2: {}", "some args");
        if false { // Enable to test assert
            scoped_assert!(false);
            scoped_assert!(false, "I failed!");
        }
        push_log_scope!("inner-scope");
        scoped_info!(target: "some-target", "2: {}", "some args");
        Foo.foo();
    }
    scoped_info!("4");
}

#[derive(Debug)]
struct Foo;

impl Foo {
    fn foo(&self) {
        push_log_scope!("{:?}-scope", self);
        scoped_info!("3");
    }
}

以下是从： cargo run --example example && RUST_LOG=example=trace target/debug/examples/example

     Running `target/debug/examples/example`
INFO:example: 1
INFO:example: outer-scope: 2: some args
INFO:example: outer-scope: inner-scope: Foo-scope: 3
INFO:example: 4