Run yarn as pre-commit hook if package.json was changed (#225)

experimental/babel-preset-env/package.json

@@ -121,6 +121,10 @@
     "test/*.js": [
       "prettier --trailing-comma all --write",
       "git add"
+    ],
+    "package.json": [
+      "node ./scripts/yarn-install.js",
+      "git add yarn.lock"
     ]
   }
 }

experimental/babel-preset-env/scripts/yarn-install.js

@@ -0,0 +1,13 @@
+"use strict";
+
+const exec = require("child_process").exec;
+
+const runIfYarn = fn => {
+  exec("yarn -V", error => {
+    if (error === null) fn();
+  });
+};
+runIfYarn(() => {
+  console.log("`package.json` was changed. Running yarn...🐈");
+  exec("yarn");
+});