feat: add log-file option (#383)

src/args.rs

@@ -197,6 +197,15 @@ pub fn build_cli() -> Command {
                 .value_name("format")
                 .help("Customize http log format"),
         )
+        .arg(
+            Arg::new("log-file")
+                .env("DUFS_LOG_FILE")
+                .hide_env(true)
+                .long("log-file")
+                .value_name("file")
+                .value_parser(value_parser!(PathBuf))
+                .help("Specify the file to save logs to, other than stdout/stderr"),
+        )
         .arg(
             Arg::new("compress")
                 .env("DUFS_COMPRESS")
@@ -280,6 +289,7 @@ pub struct Args {
     #[serde(deserialize_with = "deserialize_log_http")]
     #[serde(rename = "log-format")]
     pub http_logger: HttpLogger,
+    pub log_file: Option<PathBuf>,
     pub compress: Compress,
     pub tls_cert: Option<PathBuf>,
     pub tls_key: Option<PathBuf>,
@@ -392,6 +402,10 @@ impl Args {
             args.http_logger = log_format.parse()?;
         }
 
+        if let Some(log_file) = matches.get_one::<PathBuf>("log-file") {
+            args.log_file = Some(log_file.clone());
+        }
+
         if let Some(compress) = matches.get_one::<Compress>("compress") {
             args.compress = *compress;
         }