♲ Refactor configuration to use viper with context propagation

- Replace global ConfigPath and Overrides with viper-based configuration
- Add viper.New() to create configurable viper instances
- Store viper and unmarshaled Config struct in context for testability
- Add RetrieveFromContext and AddToContext helper functions
- Update files.Append to accept context and retrieve config from it
- Update formatters.Preferred and formatters.New to accept context
- Add PersistentPreRunE in CLI to create and configure viper instance
- Support -c flag for custom config file path
- Support -v flag for config value overrides
- Update all test files to create viper and add to context
- Remove unused config types and load functions
- Add viper as dependency with automatic env var support (MYLOG_*)

cli/config.go

@@ -32,23 +32,24 @@ var ConfigCmd = &cobra.Command{
 	RunE: func(cmd *cobra.Command, args []string) (err error) {
 		print, _ := cmd.Flags().GetBool("print")
 		if print {
-			fmt.Fprintln(cmd.OutOrStdout(), config.ConfigPath)
+			fmt.Fprintln(cmd.OutOrStdout(), config.DefaultPath())
 			return nil
 		}
 		force, _ := cmd.Flags().GetBool("force")
+		configPath := config.DefaultPath()
 		if !force {
-			_, err = os.Stat(config.ConfigPath)
+			_, err = os.Stat(configPath)
 			if !os.IsNotExist(err) {
-				return fmt.Errorf("%s already exists. Use -f to overwrite", config.ConfigPath)
+				return fmt.Errorf("%s already exists. Use -f to overwrite", configPath)
 			}
 		}
-		dir := fp.Dir(config.ConfigPath)
+		dir := fp.Dir(configPath)
 		err = os.MkdirAll(dir, 0755)
 		if err != nil {
 			return
 		}
 
-		f, err := os.Create(config.ConfigPath)
+		f, err := os.Create(configPath)
 		if err != nil {
 			return
 		}