cli: when config is invalid, use default config

When we fail to read the user's config, it seems obviously better to
use the default config than to not use it. It doesn't matter yet, but
it will matter when I've moved color configs out of `formatter.rs` and
into a `.toml` file. Without this change, we'd lose the default
coloring of the error message for config errors.

lib/src/settings.rs

@@ -18,7 +18,7 @@ use chrono::DateTime;
 
 use crate::backend::{Signature, Timestamp};
 
-#[derive(Debug, Clone, Default)]
+#[derive(Debug, Clone)]
 pub struct UserSettings {
     config: config::Config,
     timestamp: Option<Timestamp>,

src/cli_util.rs

@@ -1432,7 +1432,7 @@ pub fn create_ui() -> (Ui, Result<(), CommandError>) {
     match read_config() {
         Ok(user_settings) => (Ui::for_terminal(user_settings), Ok(())),
         Err(err) => {
-            let ui = Ui::for_terminal(UserSettings::default());
+            let ui = Ui::for_terminal(UserSettings::from_config(crate::config::default_config()));
             (ui, Err(CommandError::ConfigError(err.to_string())))
         }
     }

src/config.rs

@@ -72,7 +72,7 @@ fn env_base() -> config::Config {
     builder.build().unwrap()
 }
 
-fn default_config() -> config::Config {
+pub fn default_config() -> config::Config {
     // Syntax error in default config isn't a user error. That's why defaults are
     // loaded by separate builder.
     config::Config::builder()