git_change_type.js

const { execSync }  = require('child_process');

const files       = execSync(`git --no-pager diff --name-only HEAD HEAD~1`).toString().split('\n');
const extensions  = {}

const identity = (i) => i

const upper = (s) => s.toUpperCase()

files.forEach(f => {
  const split = f.split('.')
  const ext   = split[split.length - 1];
  
  extensions[ext] = true;
});

console.log(
  Object
    .keys(extensions)
    .filter(identity)
    .map(upper)
    .join('/')
)