Add lint-staged + husky for prettier auto-formatting on commit (facebook#1759)

Author: Kent C. Dodds

PULL_REQUEST_TEMPLATE.md

@@ -4,7 +4,5 @@ If you changed any code, there are just two more things to do:
 
 * Provide us with clear instructions on how you verified your changes work. Bonus points for screenshots!
 
-* If you changed any code, run `npm run format` in the root folder, and commit and push the changes.
-
 Happy contributing!
 -->

package.json

@@ -9,12 +9,21 @@
     "publish": "tasks/release.sh",
     "start": "node packages/react-scripts/scripts/start.js",
     "test": "node packages/react-scripts/scripts/test.js --env=jsdom",
-    "format": "prettier --trailing-comma es5 --single-quote --write 'packages/*/*.js' 'packages/*/!(node_modules)/**/*.js'"
+    "format": "prettier --trailing-comma es5 --single-quote --write 'packages/*/*.js' 'packages/*/!(node_modules)/**/*.js'",
+    "precommit": "lint-staged"
   },
   "devDependencies": {
     "eslint": "3.16.1",
+    "husky": "^0.13.2",
     "lerna": "2.0.0-beta.38",
     "lerna-changelog": "^0.2.3",
+    "lint-staged": "^3.3.1",
     "prettier": "^0.21.0"
+  },
+  "lint-staged": {
+    "*.js": [
+      "prettier --trailing-comma es5 --single-quote --write",
+      "git add"
+    ]
   }
 }