Analyse the commits on node core to see how many are doc-only, etc.

commits.js

/**
 * Plop this in your node git repo and run:
 *
 * $ node commits.js [num of commits you want to analyse (default 1000)]
 */

var exec = require('child_process').exec;

function gitDiffTree(commit, recursive, cb) {
    exec('git diff-tree --name-only --no-commit-id ' + (recursive ? '-r ' : '') + commit, function(err, data) {
        if (err) return cb(err);
        cb(null, data.trim().split('\n'));
    });
}


var onlyDocs = 0, onlyNonDocs = 0, docsAndNonDocs = 0;
var onlyApiDocs = 0, onlyNonApiDocs = 0, apiAndNonApiDocs = 0;
function getCommits(i) {
    process.stdout.write('\033[2K\033[200Dcommits left to process: '+i);
    i--;
    if (i === -1) {
        return processResults();
    }
    gitDiffTree('HEAD~'+i, false, function(err, list){
        if (err) throw err;
        if (list.length === 1 && list[0] === 'doc') {
            onlyDocs++;
            return processOnlyDocs(i, function(){
                getCommits(i);
            });

        } else if (list.length > 0 && list.indexOf('doc') === -1) {
            onlyNonDocs++;
        } else {
            docsAndNonDocs++;
        }
        getCommits(i);
    });
}

function processOnlyDocs(i, cb) {
    gitDiffTree('HEAD~'+i, true, function(err, list) {
        if (err) throw err;
        var hasApiDoc = false, hasNonApiDoc = false;
        list.forEach(function(item){
            if (/^doc\/api\//.test(item)) {
                hasApiDoc = true;
            } else {
                hasNonApiDoc = true;
            }
        });
        if (hasApiDoc && !hasNonApiDoc) {
            onlyApiDocs++;
        } else if (!hasApiDoc && hasNonApiDoc) {
            onlyNonApiDocs++;
        } else {
            apiAndNonApiDocs++;
        }
        cb();
    });
}

function processResults() {
    process.stdout.write('\033[2K\033[200DDone!\n\n');
    console.log('In the last', totalCommits, 'commits:');
    console.log('---');
    console.log('both docs and non-docs:          ', percentage(docsAndNonDocs));
    console.log('non-docs only:                   ', percentage(onlyNonDocs));
    console.log('docs only:                       ', percentage(onlyDocs));
    console.log(' -> both api and non-api:        ', percentage(apiAndNonApiDocs));
    console.log(' -> non-api only (minutes, etc): ', percentage(onlyNonApiDocs));
    console.log(' -> api only:                    ', percentage(onlyApiDocs));
}

function percentage (num) {
    return num+'   ('+Math.round(10000*num/totalCommits)/100+'%)';
}

var totalCommits = process.argv[2] ?
                   (isNaN(+process.argv[2]) ? 1000 : +process.argv[2]) :
                   1000;

getCommits(totalCommits);