feat: add config system with --config argument and priority-based configuration

Co-authored-by: aider (openai/andrew/openrouter/anthropic/claude-sonnet-4) <aider@aider.chat>

src/config.rs

@@ -0,0 +1,96 @@
+use std::path::PathBuf;
+use std::fs;
+use anyhow::{Result, Context};
+use serde::{Deserialize, Serialize};
+use log::debug;
+
+#[derive(Debug, Clone, Deserialize, Serialize, Default)]
+pub struct Config {
+    pub dir: Option<PathBuf>,
+    pub list_format: Option<String>,
+    pub human_readable: Option<bool>,
+    pub server: Option<ServerConfig>,
+    pub compression_plugin: Option<CompressionPluginConfig>,
+    pub meta_plugins: Option<Vec<MetaPluginConfig>>,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct ServerConfig {
+    pub address: Option<String>,
+    pub port: Option<u16>,
+    pub password_file: Option<PathBuf>,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct CompressionPluginConfig {
+    pub name: String,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct MetaPluginConfig {
+    pub name: String,
+}
+
+impl Config {
+    /// Load configuration from a file
+    pub fn from_file(path: &PathBuf) -> Result<Self> {
+        debug!("CONFIG: Loading config from {:?}", path);
+        
+        if !path.exists() {
+            debug!("CONFIG: Config file does not exist, using defaults");
+            return Ok(Config::default());
+        }
+
+        let content = fs::read_to_string(path)
+            .with_context(|| format!("Failed to read config file: {:?}", path))?;
+        
+        let config: Config = serde_yaml::from_str(&content)
+            .with_context(|| format!("Failed to parse config file: {:?}", path))?;
+        
+        debug!("CONFIG: Loaded config: {:?}", config);
+        Ok(config)
+    }
+
+    /// Get the default config file path
+    pub fn default_config_path() -> Result<PathBuf> {
+        let xdg_dirs = xdg::BaseDirectories::with_prefix("keep")?;
+        Ok(xdg_dirs.get_config_home().join("config.yml"))
+    }
+
+    /// Read password from password_file if configured
+    pub fn get_server_password(&self) -> Result<Option<String>> {
+        if let Some(server) = &self.server {
+            if let Some(password_file) = &server.password_file {
+                debug!("CONFIG: Reading password from file: {:?}", password_file);
+                let password = fs::read_to_string(password_file)
+                    .with_context(|| format!("Failed to read password file: {:?}", password_file))?
+                    .trim()
+                    .to_string();
+                return Ok(Some(password));
+            }
+        }
+        Ok(None)
+    }
+
+    /// Merge this config with another, giving priority to the other config
+    pub fn merge_with(&mut self, other: &Config) {
+        if other.dir.is_some() {
+            self.dir = other.dir.clone();
+        }
+        if other.list_format.is_some() {
+            self.list_format = other.list_format.clone();
+        }
+        if other.human_readable.is_some() {
+            self.human_readable = other.human_readable;
+        }
+        if other.server.is_some() {
+            self.server = other.server.clone();
+        }
+        if other.compression_plugin.is_some() {
+            self.compression_plugin = other.compression_plugin.clone();
+        }
+        if other.meta_plugins.is_some() {
+            self.meta_plugins = other.meta_plugins.clone();
+        }
+    }
+}