automatically update cli doc on every version bump

docs/cli/index.md

@@ -452,4 +452,5 @@ Config Files:
   Run 'tap --dump-config' for a listing of what can be set in that file. Each of
   the keys corresponds to one of the options above.
 
+
 ```

docs/cli/index.template.js

@@ -0,0 +1,7 @@
+#!/usr/bin/env node
+const fs = require('fs')
+const template = fs.readFileSync(__dirname + '/index.template.md', 'utf8')
+const {spawnSync} = require('child_process')
+const bin = require.resolve('../../bin/run.js')
+const usage = spawnSync(process.execPath, [bin, '-h']).output.join('')
+fs.writeFileSync(__dirname + '/index.md', template.replace(/\$\{USAGE\}/, usage))

docs/cli/index.template.md

@@ -0,0 +1,12 @@
+---
+layout: layout
+title: CLI
+---
+
+# CLI
+
+You can get help on tap's command line interface by running `tap -h`.
+
+```
+${USAGE}
+```

package.json

@@ -72,7 +72,7 @@
     "posttest": "rm -rf cli-tests-*",
     "postunit": "npm run posttest",
     "t": "node bin/run.js test -J -sfails.txt",
-    "preversion": "npm test",
+    "preversion": "npm test && node docs/cli/index.template.js",
     "postversion": "npm publish",
     "postpublish": "git push origin --follow-tags"
   },