Merge branch 'verbosity' into 'master'

Add support for configuring the verbosity of the logger from CLI opts

See merge request !1

src/cli.rs

 use std::path::PathBuf;
 
 use clap::{Clap, IntoApp};
+use log::LevelFilter;
 use serde::de::DeserializeOwned;
 use thiserror::Error;
 
@@ -16,9 +17,31 @@ pub enum CliError {
 
 pub trait AppOpts: Clap {
     fn try_init() -> Result<Self, CliError> {
-        pretty_env_logger::init();
+        let result = Self::try_parse().map_err(CliError::ArgParse);
 
-        Self::try_parse().map_err(CliError::ArgParse)
+        match &result {
+            Ok(result) => {
+                try_init_pretty_logger(
+                    result.get_log_environment_variable_name(),
+                    result.get_log_level_filter(),
+                )
+                .unwrap();
+            }
+            Err(_) => {
+                // Initialize the logger with defaults.
+                pretty_env_logger::init();
+            }
+        }
+
+        result
+    }
+
+    fn get_log_level_filter(&self) -> Option<LevelFilter> {
+        None
+    }
+
+    fn get_log_environment_variable_name(&self) -> Option<&str> {
+        None
     }
 }
 
@@ -36,3 +59,20 @@ pub trait ConfigurableAppOpts<C: DeserializeOwned>: AppOpts {
 
     fn get_additional_config_paths(&self) -> Vec<PathBuf>;
 }
+
+fn try_init_pretty_logger(
+    environment_variable_name: Option<&str>,
+    level_filter_override: Option<LevelFilter>,
+) -> Result<(), log::SetLoggerError> {
+    let mut builder = pretty_env_logger::formatted_builder();
+
+    if let Some(level_filter_override) = level_filter_override {
+        builder.filter(None, level_filter_override);
+    }
+
+    if let Ok(s) = ::std::env::var(environment_variable_name.unwrap_or("RUST_LOG")) {
+        builder.parse_filters(&s);
+    }
+
+    builder.try_init()
+}