add tracing_journald support for linux (#407)

all comtrya log

```
$ journalctl -t comtrya
```

filter by manifest
```
$ journalctl F_MANIFEST=github
```

filter by action
```
$ journalctl F_ACTION=github.binary
```

app/Cargo.toml

@@ -17,6 +17,7 @@ rhai = { version = "1.17", features = ["serde"] }
 strip-ansi-escapes = "0.2"
 structopt = { version = "0.3", features = ["paw"] }
 tracing = "0.1"
+tracing-journald = "0.3.0"
 tracing-subscriber = "0.3"
 update-informer = "1.1"
 

app/src/main.rs

@@ -1,11 +1,13 @@
+use std::io;
+
 use commands::ComtryaCommand;
 
 use comtrya_lib::contexts::build_contexts;
 use comtrya_lib::contexts::Contexts;
 use comtrya_lib::manifests;
 use structopt::StructOpt;
-use tracing::{error, Level, Subscriber};
-use tracing_subscriber::FmtSubscriber;
+use tracing::{error, Level};
+use tracing_subscriber::{fmt::writer::MakeWriterExt, layer::SubscriberExt, FmtSubscriber};
 
 mod commands;
 mod config;
@@ -58,26 +60,34 @@ pub(crate) fn execute(runtime: Runtime) -> anyhow::Result<()> {
  }
 }
 
-fn configure_subscriber(args: &GlobalArgs) -> impl Subscriber {
+fn configure_tracing(args: &GlobalArgs) {
+ let stdout_writer = match args.verbose {
+ 0 => io::stdout.with_max_level(tracing::Level::INFO),
+ 1 => io::stdout.with_max_level(tracing::Level::DEBUG),
+ _ => io::stdout.with_max_level(tracing::Level::TRACE),
+ };
+
  let builder = FmtSubscriber::builder()
- .with_max_level(Level::INFO)
+ .with_max_level(Level::TRACE)
  .with_ansi(!args.no_color)
  .with_target(false)
+ .with_writer(stdout_writer)
  .without_time();
 
- match args.verbose {
- 0 => builder,
- 1 => builder.with_max_level(Level::DEBUG),
- _ => builder.with_max_level(Level::TRACE),
+ #[cfg(target_os = "linux")]
+ if let Ok(layer) = tracing_journald::layer() {
+ tracing::subscriber::set_global_default(builder.finish().with(layer))
+ .expect("Unable to set a global subscriber");
+ return;
  }
- .finish()
+
+ tracing::subscriber::set_global_default(builder.finish())
+ .expect("Unable to set a global subscriber");
 }
 
 #[paw::main]
 fn main(args: GlobalArgs) -> anyhow::Result<()> {
- let subscriber = configure_subscriber(&args);
-
- tracing::subscriber::set_global_default(subscriber).expect("setting default subscriber failed");
+ configure_tracing(&args);
 
  let config = match load_config(args.clone()) {
  Ok(config) => config,