perf: avoid holding async mutex guards across await points

tokio recommends using a sync mutex with a notifier instead of the
async mutex where possible. Rust forbids holding a sync mutex guard
across await points so we can prevent a potential deadlock this way.

This adds a custom channel based on the tokio mpmc example for
handling gvfs events from callbacks to avoid the async mutex
requirement. Messages are held in a `VecDeque` behind a sync mutex
and the receiver will get notified via the notifier when a message
is added to the queue.

Weak references used in gio callbacks in case the sender is dropped
by the application.

src/lib.rs

@@ -8,6 +8,7 @@ use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
 use app::{App, Flags};
 pub mod app;
 mod archive;
+pub mod channel;
 pub mod clipboard;
 mod context_action;
 use config::Config;
@@ -136,7 +137,7 @@ pub fn main() -> Result<(), Box<dyn std::error::Error>> {
         .event_format(log_format);
 
     tracing_subscriber::registry()
-        .with(tracing_subscriber::EnvFilter::from_env("RUST_LOG"))
+        .with(tracing_subscriber::EnvFilter::from_default_env())
         .with(log_layer)
         .init();