get-makefile-rules.js

#!/usr/bin/env node

const {f = 'Makefile', _} = require('minimist')(process.argv.slice(2))
const fs = require('fs')
const parseMakefileRules = require('@quarterto/parse-makefile-rules')

const formatBody = body => body.replace(/^/mg, '\t')

const formatRule = (rule, body) => body && `${rule}:
${formatBody(body)}
`;

const formatRules = (names, rules) =>
    names.length === 1? rules[names[0]]
  : /* otherwise     */ names.map(
      name => formatRule(name, rules[name])
    ).filter(Boolean).join('\n')

const makefile = fs.readFileSync(f, 'utf8')
const parsedRules = parseMakefileRules(makefile)

const rules = _.length?        _
            :  /* otherwise */ Object.keys(parsedRules)

console.log(
  formatRules(
    rules,
    parsedRules
  ) || process.exit(1)
)