rename --config to --option

README.md

@@ -140,7 +140,7 @@ Usage: lambroll <command> [flags]
 
 Flags:
   -h, --help                              Show context-sensitive help.
-      --config=STRING                     config file path ($LAMBROLL_CONFIG)
+      --option=STRING                     option file path ($LAMBROLL_OPTION)
       --function=STRING                   Function file path ($LAMBROLL_FUNCTION)
       --log-level="info"                  log level (trace, debug, info, warn, error) ($LAMBROLL_LOGLEVEL)
       --[no-]color                        enable colored output ($LAMBROLL_COLOR)
@@ -201,7 +201,7 @@ Run "lambroll <command> --help" for more information on a command.
 
 lambroll has global flags for all commands.
 
-These flags can be set by environment variables or option file (`--config` or `lambroll.json` or `lambroll.jsonnet`).
+These flags can be set by environment variables or option file (`--option`).
 
 #### Environment variables
 
@@ -211,9 +211,9 @@ See the above usage for the environment variable names.
 
 #### Option file
 
-`--config=filename` or `lambroll.json` or `lambroll.jsonnet` can be used as an option file.
+`--option=filename` can be used as an option file.
 
-If the option file is found in the current directory, lambroll reads the file and applies to the default values of global flags.
+If the option file is specified, lambroll reads the file and applies to the default values of global flags.
 
 ```jsonnet
 {