Git log in JSON format

1.README.md

Get Git log in JSON format

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},'

The only information that aren't fetched are:

• %B: raw body (unwrapped subject and body)
• %GG: raw verification message from GPG for a signed commit

The format is applied to each line, so once you get all the lines, you need to remove the trailing , and wrap them around an Array.

git log pretty format source: http://git-scm.com/docs/pretty-formats

2.Example.md

Here is an example in Javascript based on a package I'm working on for Atom:

var 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},';

var commits = [];

new BufferedProcess({
    command: 'git',
    args: [
        'log',
        '--pretty=format:' + format
    ],
    stdout: function (chunk) { commits += chunk },
    exit: function (code) {
        if (code === 0) {
            var result = JSON.parse('[' + commits.slice(0, -1) + ']');

            console.log(result); // valid JSON array
        }
    }
});

The commit hash itself cannot be found inside the commit (since it is calculated from the commit file). So potentially, it could be used as a delimiter between commit fields. There should not be a risk of collision, unless I am missing something.

In that case, something like git log --format="%H#%s%H%b%H" would be all textual and parsable.

Example implementation:

function parseLog(log: string) {
  const commits: { hash: string; summary: string; body: string }[] = [];

  while (log.length) {
    const delimiter = log.indexOf("#");
    if (delimiter === -1) throw new Error(`Cannot parse commit log`);
    const hash = log.slice(0, delimiter);
    const [summary, body, rest] = log.slice(hash.length + 1).split(hash, 7);
    if (summary === undefined || body === undefined) {
      throw new Error(`Cannot parse commit log`);
    }
    log = rest?.trimStart() ?? "";
    commits.push({ hash, summary, body });
  }

  return commits;
}

Ref names (branches, tags and alike) are not part of the commit, so their names could collide, but they are easier to delimiter for.