app(doc): well... write the docs

crates/app/src/config.rs

@@ -14,6 +14,7 @@ pub struct Config {
 }
 
 impl Config {
+    /// Get the configs from all possible places (args, file, env...)
     pub fn read() -> Self {
         let args = Args::parse();
         let config_path = if let Some(config_path) = args.config_path {
@@ -22,6 +23,7 @@ impl Config {
             find_config_file()
         };
 
+        // try to read a maybe existing config file
         let file_config = if let Ok(config_path) = config_path {
             let file_config = Configs::read(config_path);
 
@@ -52,13 +54,22 @@ impl Config {
 }
 
 pub mod error {
+    /// Errors that can occur when reading configs
     #[derive(Debug)]
     pub enum ConfigError {
+        /// The config dir doesn't exist
         NoConfigDir,
+        /// We didn't find a config file in the config dir
         NoConfigFileFound,
+        /// An io error happened while reading/opening it!
         IoError(std::io::Error),
+        /// The given extension (via an argument) isn't known.
+        ///
+        /// Occurs if the extension is neither `.json` nor `.ron` (including if there is no extension, in which case this will be `None`).
         UnknownExtension(Option<String>),
+        /// Wrapper around an `Error` from `serde_json`
         SerdeJsonError(serde_json::Error),
+        /// Wrapper around a `SpannedError` from `ron`
         SerdeRonError(ron::error::SpannedError),
     }