git log in JSON - send changelog to browser

Question

In order to know what's actually been committed to a project in production, we are going to display the Git log to admins - this serve as a makeshift changelog.

I have this routine on a Node.js Express server:

 router.get('/changelog/json', ac.allow('ROLE_ADMIN'), function (req, res, next) {

  const k = cp.spawn('bash');

  k.stdin.write('git log --pretty=format:\'{%n  "commit": "%H",%n  "abbreviated_commit": "%h",%n  "tree": "%T",%n  "abbreviated_tree": "%t",%n  "parent": "%P",%n  "abbreviated_parent": "%p",%n  "refs": "%D",%n  "encoding": "%e",%n  "subject": "%s",%n  "sanitized_subject_line": "%f",%n  "body": "%b",%n  "commit_notes": "%N",%n  "verification_flag": "%G?",%n  "signer": "%GS",%n  "signer_key": "%GK",%n  "author": {%n    "name": "%aN",%n    "email": "%aE",%n    "date": "%aD"%n  },%n  "commiter": {%n    "name": "%cN",%n    "email": "%cE",%n    "date": "%cD"%n  }%n},\'\n')

  k.stdin.end();
  k.stdout.pipe(res);


});

this sort of works, but we don't actually get a JSON array, we just get comma separate JSON strings.

I got this info form here: https://gist.github.com/varemenos/e95c2e098e657c7688fd https://git-scm.com/docs/pretty-formats

does anyone know how I can construct a JSON array from the stdout from the Git command?

I tried this:

router.get('/json', ac.allow('ROLE_ADMIN'), function (req, res, next) {

  const p = createParser();

  const k = cp.spawn('bash', [], {
    cwd: global.cdtProjectRoot
  });

  const items = [];

  k.stdin.write('git log --pretty=format:\'{%n  "commit": "%H",%n  "abbreviated_commit": "%h",%n  "tree": "%T",%n  "abbreviated_tree": "%t",%n  "parent": "%P",%n  "abbreviated_parent": "%p",%n  "refs": "%D",%n  "encoding": "%e",%n  "subject": "%s",%n  "sanitized_subject_line": "%f",%n  "body": "%b",%n  "commit_notes": "%N",%n  "verification_flag": "%G?",%n  "signer": "%GS",%n  "signer_key": "%GK",%n  "author": {%n    "name": "%aN",%n    "email": "%aE",%n    "date": "%aD"%n  },%n  "commiter": {%n    "name": "%cN",%n    "email": "%cE",%n    "date": "%cD"%n  }%n},\'\n')
  k.stdin.end();

  k.stdout.pipe(p).on('data', function (d) {
     // d would be a parsed JSON object
    items.push(d);
  })
  .once('error', next)
  .once('end', function () {

    res.json({
      success: items
    })
  })

});

My parser transform works, because I use it in another project, so it's something about the format of the JSON coming from the stdout that's causing the problem - the 'data' event handler never sees any data.

Answer 1

This worked for me, I had to improve the git log format option:

router.get('/json', ac.allow('ROLE_ADMIN'), function (req, res, next) {

  const p = createParser();
  const k = cp.spawn('bash');

  let items = [];

  k.stdin.write(`git log -300 --pretty=format:'{"commit":"%H","sanitized_subject_line":"%f","commit_notes":"%N","author":"%aN","date":"%aD"}'`);
  k.stdin.end('\n');

  k.stdout.pipe(p).on('data', function (d) {
    items.push(JSON.parse(d));
  })
  .once('error', next)
  .once('end', function () {

    res.json({
      success: items
    })
  })

});

createParser looks like this:

const stream = require("stream");

exports.createParser = function () {

  let lastLineData = '';

  let strm = new stream.Transform({

    objectMode: true,

    transform: function (chunk, encoding, cb) {
      let _this = this;
      let data = String(chunk);
      if (lastLineData) {
        data = lastLineData + data;
      }
      let lines = data.split('\n');
      lastLineData = lines.splice(lines.length - 1, 1)[0];
      lines.forEach(function (l) {
        l && _this.push(l);
      });
      cb();
    },

    flush: function (cb) {
      if (lastLineData) {
        this.push(lastLineData);
      }
      lastLineData = '';
      cb();
    }
  });

  return strm;
};

this might barf if there are certain characters in the git log fields, like Author, but I think the built-in field "sanitized_subject_line" will save our skin a bit when it comes to removing bad chars from commit messages.