Clarify directory exclusions in glob patterns

Fixes #1750.

Author: Briantmorr

readme.md

@@ -237,12 +237,15 @@ AVA automatically removes unrelated lines in stack traces, allowing you to find
 
 All of the CLI options can be configured in the `ava` section of your `package.json`. This allows you to modify the default behavior of the `ava` command, so you don't have to repeatedly type the same options on the command prompt.
 
+To ignore a file or directory, prefix the pattern with an `!` (exclamation mark).
+
 ```json
 {
 	"ava": {
 		"files": [
-			"my-test-folder/*.js",
-			"!**/not-this-file.js"
+			"my-test-directory/**/*.js",
+			"!my-test-directory/exclude-this-directory/**/*.js",
+			"!**/exclude-this-file.js"
 		],
 		"source": [
 			"**/*.{js,jsx}",