Feature: Config file

Read flags for several params from config file.

This was a popular requested feature (many people want to run with -r on
by default).

src/config.rs

@@ -0,0 +1,68 @@
+use clap::ArgMatches;
+use config_file::FromConfigFile;
+use serde::Deserialize;
+use std::path::Path;
+use std::path::PathBuf;
+
+#[derive(Deserialize, Default)]
+#[serde(rename_all = "kebab-case")]
+#[serde(deny_unknown_fields)]
+pub struct Config {
+    pub display_full_paths: Option<bool>,
+    pub display_apparent_size: Option<bool>,
+    pub reverse: Option<bool>,
+    pub no_colors: Option<bool>,
+    pub no_bars: Option<bool>,
+    pub skip_total: Option<bool>,
+    pub ignore_hidden: Option<bool>,
+    pub iso: Option<bool>,
+}
+
+impl Config {
+    pub fn get_no_colors(&self, options: &ArgMatches) -> bool {
+        Some(true) == self.no_colors || options.is_present("no_colors")
+    }
+    pub fn get_apparent_size(&self, options: &ArgMatches) -> bool {
+        Some(true) == self.display_apparent_size || options.is_present("display_apparent_size")
+    }
+    pub fn get_ignore_hidden(&self, options: &ArgMatches) -> bool {
+        Some(true) == self.ignore_hidden || options.is_present("ignore_hidden")
+    }
+    pub fn get_full_paths(&self, options: &ArgMatches) -> bool {
+        Some(true) == self.display_full_paths || options.is_present("display_full_paths")
+    }
+    pub fn get_reverse(&self, options: &ArgMatches) -> bool {
+        Some(true) == self.reverse || options.is_present("reverse")
+    }
+    pub fn get_no_bars(&self, options: &ArgMatches) -> bool {
+        Some(true) == self.no_bars || options.is_present("no_bars")
+    }
+    pub fn get_iso(&self, options: &ArgMatches) -> bool {
+        Some(true) == self.iso || options.is_present("iso")
+    }
+    pub fn get_skip_total(&self, options: &ArgMatches) -> bool {
+        Some(true) == self.skip_total || options.is_present("skip_total")
+    }
+}
+
+fn get_config_locations(base: &Path) -> Vec<PathBuf> {
+    vec![
+        base.join(".dust.toml"),
+        base.join(".config").join("dust").join("config.toml"),
+    ]
+}
+
+pub fn get_config() -> Config {
+    if let Some(home) = directories::BaseDirs::new() {
+        for path in get_config_locations(home.home_dir()) {
+            if path.exists() {
+                if let Ok(config) = Config::from_config_file(path) {
+                    return config;
+                }
+            }
+        }
+    }
+    Config {
+        ..Default::default()
+    }
+}