Use a config file format like ssh's

Cargo.toml

@@ -32,7 +32,7 @@ derive-deftly = "0.14.2"
 dirs = "5.0.1"
 dns-lookup = "2.0.4"
 expanduser = "1.2.2"
-figment = { version = "0.10.19", features = ["toml"] }
+figment = { version = "0.10.19" }
 futures-util = { version = "0.3.31", default-features = false }
 gethostname = "0.5.0"
 glob = "0.3.1"
@@ -74,7 +74,6 @@ rand = "0.8.5"
 serde_json = "1.0.133"
 serde_test = "1.0.177"
 tempfile = "3.14.0"
-toml = "0.8.19"
 
 [lints.rust]
 dead_code = "warn"

src/cli/args.rs

@@ -6,7 +6,7 @@ use clap::{ArgAction::SetTrue, Args as _, FromArgMatches as _, Parser};
 use crate::{config::Manager, util::AddressFamily};
 
 /// Options that switch us into another mode i.e. which don't require source/destination arguments
-pub(crate) const MODE_OPTIONS: &[&str] = &["server", "help_buffers", "show_config", "config_files"];
+pub(crate) const MODE_OPTIONS: &[&str] = &["server", "help_buffers", "config_files", "show_config"];
 
 #[derive(Debug, Parser, Clone)]
 #[command(
@@ -44,7 +44,14 @@ pub(crate) struct CliArgs {
     )]
     pub server: bool,
 
-    /// Outputs the configuration, then exits
+    /// Outputs the configuration, then exits.
+    ///
+    /// If a remote `SOURCE` or `DESTINATION` argument is given, outputs the configuration we would use
+    /// for operations to that host.
+    ///
+    /// If not, outputs only global settings from configuration, which may be overridden in
+    /// `Host` blocks in configuration files.
+    ///
     #[arg(long, help_heading("Configuration"))]
     pub show_config: bool,
     /// Outputs the paths to configuration file(s), then exits
@@ -93,20 +100,22 @@ impl CliArgs {
             CliArgs::from_arg_matches(&cli.get_matches_from(std::env::args_os())).unwrap();
         // Custom logic: '-4' and '-6' convenience aliases
         if args.ipv4_alias__ {
-            args.config.address_family = Some(AddressFamily::V4);
+            args.config.address_family = Some(AddressFamily::Inet);
         } else if args.ipv6_alias__ {
-            args.config.address_family = Some(AddressFamily::V6);
+            args.config.address_family = Some(AddressFamily::Inet6);
         }
         args
     }
 }
 
-impl From<&CliArgs> for Manager {
-    /// Merge options from the CLI into the structure.
-    /// Any new option packs (_Optional structs) need to be added here.
-    fn from(value: &CliArgs) -> Self {
-        let mut mgr = Manager::new();
+impl TryFrom<&CliArgs> for Manager {
+    type Error = anyhow::Error;
+
+    fn try_from(value: &CliArgs) -> Result<Self, Self::Error> {
+        let host = value.client_params.remote_host_lossy()?;
+
+        let mut mgr = Manager::standard(host.as_deref());
         mgr.merge_provider(&value.config);
-        mgr
+        Ok(mgr)
     }
 }

src/cli/cli_main.rs

@@ -3,10 +3,7 @@
 
 use std::process::ExitCode;
 
-use super::{
-    args::CliArgs,
-    styles::{ERROR_S, INFO_S},
-};
+use super::{args::CliArgs, styles::ERROR_S};
 use crate::{
     client::{client_main, Parameters as ClientParameters, MAX_UPDATE_FPS},
     config::{Configuration, Manager},
@@ -58,19 +55,19 @@ pub async fn cli() -> anyhow::Result<ExitCode> {
     }
 
     // Now fold the arguments in with the CLI config (which may fail)
-    let config_manager = Manager::from(&args);
+    let config_manager = match Manager::try_from(&args) {
+        Ok(m) => m,
+        Err(err) => {
+            eprintln!("{}: {err}", "ERROR".style(*ERROR_S));
+            return Ok(ExitCode::FAILURE);
+        }
+    };
 
     let config = match config_manager.get::<Configuration>() {
         Ok(c) => c,
         Err(err) => {
-            println!("{}: Failed to parse configuration", "ERROR".style(*ERROR_S));
-            if err.count() == 1 {
-                println!("{err}");
-            } else {
-                for (i, e) in err.into_iter().enumerate() {
-                    println!("{}: {e}", (i + 1).style(*INFO_S));
-                }
-            }
+            eprintln!("{}: Failed to parse configuration", "ERROR".style(*ERROR_S));
+            err.into_iter().for_each(|e| eprintln!("{e}"));
             return Ok(ExitCode::FAILURE);
         }
     };
@@ -84,10 +81,7 @@ pub async fn cli() -> anyhow::Result<ExitCode> {
     .inspect_err(|e| eprintln!("{e:?}"))?;
 
     if args.show_config {
-        println!(
-            "{}",
-            config_manager.to_display_adapter::<Configuration>(true)
-        );
+        println!("{}", config_manager.to_display_adapter::<Configuration>());
         Ok(ExitCode::SUCCESS)
     } else if args.server {
         let _span = error_span!("REMOTE").entered();

src/client/options.rs

@@ -54,8 +54,7 @@ pub struct Parameters {
     ///
     /// Exactly one of source and destination must be remote.
     #[arg(
-        conflicts_with_all(crate::cli::MODE_OPTIONS),
-        required = true,
+        required_unless_present_any(crate::cli::MODE_OPTIONS),
         value_name = "SOURCE"
     )]
     pub source: Option<FileSpec>,
@@ -66,8 +65,7 @@ pub struct Parameters {
     ///
     /// Exactly one of source and destination must be remote.
     #[arg(
-        conflicts_with_all(crate::cli::MODE_OPTIONS),
-        required = true,
+        required_unless_present_any(crate::cli::MODE_OPTIONS),
         value_name = "DESTINATION"
     )]
     pub destination: Option<FileSpec>,
@@ -98,3 +96,27 @@ impl TryFrom<&Parameters> for CopyJobSpec {
         })
     }
 }
+
+impl Parameters {
+    /// A best-effort attempt to extract a single remote host string from the parameters.
+    ///
+    /// # Output
+    /// If neither source nor dest are present, Ok("")
+    /// If at most one of source and dest contains a remote host, Ok(<host>)
+    ///
+    /// # Errors
+    /// If both source and dest contain a remote host, Err("Only one remote file argument is supported")
+    pub(crate) fn remote_host_lossy(&self) -> anyhow::Result<Option<String>> {
+        let src_host = self.source.as_ref().and_then(|fs| fs.host.as_ref());
+        let dst_host = self.destination.as_ref().and_then(|fs| fs.host.as_ref());
+        Ok(if let Some(src_host) = src_host {
+            if dst_host.is_some() {
+                anyhow::bail!("Only one remote file argument is supported");
+            }
+            Some(src_host.to_string())
+        } else {
+            // Destination without source would be an exotic situation, but do our best anyway:
+            dst_host.map(std::string::ToString::to_string)
+        })
+    }
+}

src/client/ssh.rs

@@ -43,7 +43,7 @@ impl ConfigFile {
             }
             return None;
         }
-        let mut parser = match Parser::for_path(path, self.user) {
+        let parser = match Parser::for_path(path, self.user) {
             Ok(p) => p,
             Err(e) => {
                 // file permissions issue?
@@ -52,7 +52,7 @@ impl ConfigFile {
             }
         };
         let data = match parser
-            .parse_file_for(host)
+            .parse_file_for(Some(host))
             .with_context(|| format!("reading configuration file {path:?}"))
         {
             Ok(data) => data,