Remove --no-cache CLI flag

This is a weird flag to use when invoking AVA, since it causes AVA to
use a temporary directory as the cache. Removing the flag will cause AVA
to revert to the regular cache directory.

Document the `cache` configuration option (non-CLI).

lib/cli.js

@@ -36,7 +36,6 @@ exports.run = () => { // eslint-disable-line complexity
 		  --concurrency, -c       Max number of test files running at the same time (Default: CPU cores)
 		  --verbose, -v           Enable verbose output
 		  --tap, -t               Generate TAP output
-		  --no-cache              Disable the compiler cache
 		  --color                 Force color output
 		  --no-color              Disable color output
 
@@ -92,10 +91,6 @@ exports.run = () => { // eslint-disable-line complexity
 				alias: 't',
 				default: conf.tap
 			},
-			cache: {
-				type: 'boolean',
-				default: conf.cache !== false
-			},
 			color: {
 				type: 'boolean',
 				default: 'color' in conf ? conf.color : require('supports-color').stdout !== false
@@ -151,7 +146,7 @@ exports.run = () => { // eslint-disable-line complexity
 		failWithoutAssertions: conf.failWithoutAssertions !== false,
 		serial: conf.serial,
 		require: arrify(conf.require),
-		cacheEnabled: conf.cache,
+		cacheEnabled: conf.cache !== false,
 		compileEnhancements: conf.compileEnhancements !== false,
 		match,
 		babelConfig,

readme.md

@@ -158,7 +158,6 @@ $ ava --help
     --concurrency, -c       Max number of test files running at the same time (Default: CPU cores)
     --verbose, -v           Enable verbose output
     --tap, -t               Generate TAP output
-    --no-cache              Disable the compiler cache
     --color                 Force color output
     --no-color              Disable color output
 
@@ -253,6 +252,7 @@ To ignore a file or directory, prefix the pattern with an `!` (exclamation mark)
 			"*oo",
 			"!foo"
 		],
+		"cache": true,
 		"concurrency": 5,
 		"failFast": true,
 		"failWithoutAssertions": false,
@@ -277,6 +277,7 @@ Arguments passed to the CLI will always take precedence over the configuration i
 - `files`: file & directory paths and glob patterns that select which files AVA will run tests from. Only files with a `.js` extension are used. Files with an underscore prefix are ignored. All `.js` files in selected directories are run
 - `source`: files that, when changed, cause tests to be re-run in watch mode. See the [watch mode recipe for details](https://github.com/avajs/ava/blob/master/docs/recipes/watch-mode.md#source-files-and-test-files)
 - `match`: not typically useful in the `package.json` configuration, but equivalent to [specifying `--match` on the CLI](#running-tests-with-matching-titles)
+- `cache`: cache compiled test and helper files under `node_modules/.cache/ava`. If `false`, files are cached in a temporary directory instead
 - `failFast`: stop running further tests once a test fails
 - `failWithoutAssertions`: if `false`, does not fail a test if it doesn't run [assertions](#assertions)
 - `tap`: if `true`, enables the [TAP reporter](#tap-reporter)