Re-indents given files to have 4 spaces of indentation

reindent.js

var fs = require('fs');
var path = require('path');

process.argv.slice(2).forEach(function (file) {
    var content = fs.readFileSync(file).toString();
    var indent = get_indentation(content);
    if (isNaN(indent)) throw new Error('NaN:' + file);
    if (!indent || indent === 4) {
        console.log('Skip:', file);
        return;
    }
    console.log('Reindent from %d:', indent, file);
    fs.writeFileSync(file, reindent(indent, 4, content));
});

function repeat (times, str) {
    var result = '';
    for (var index = 0; index < times; ++index) { result = result + str; }
    return result;
}

function reindent (from, to, content) {
    var indent = repeat(to, ' ');
    var reg = new RegExp('^' + repeat(from, '\\s'));
    return content.split('\n').map(function (line) {
        line = line.replace(/\s+$/, '');
        var match = line.match(/^\s+/);
        if (match && match.length) {
            line = repeat(Math.ceil(match[0].length / from), indent) + line.slice(match[0].length);
        }
        return line;
    }).join('\n');
}

function get_indentation (str) {
    var indent = {};
    str.split('\n').forEach(function (line, index) {
        var match = line.replace(/\t/g, '  ').match(/^\s+/);
        if (!match || !match.length || match[0].length % 2 !== 0) return;
        indent[match[0].length] = indent[match[0].length] || [];
        indent[match[0].length].push(index);
    });
    var indent_size = Object.keys(indent).reduce(function (sum, key) {
        return gcd(sum, parseInt(key, 10));
    }, 0);

    return indent_size;
}

function gcd (a, b) {
    if (!b) return a;
    return gcd(b, a % b);
};