Not fully tested, but should work.

Comigoji Changelog

This CLI app is designed to generate changelogs for one or more repos at once. By default, repos should convey to Comigoji commit message guidelines, and can use both Vanilla and Gitmoji-like flavors out-of-the-box. This can be configured, though, and be applicable to other commit message guidelines as long as they have distinct prefixes in their subjects.

Usage

// yourProject/comigojiChangelog.js
// Can also be a static .json file

const since = new Date('2019-09-25T10:15:11+12:00');
module.exports = {
    repos: [{
        since,
        repo: './repo1',
        branch: 'develop'
    }, {
        since,
        repo: '/home/user/repo2',
        branch: 'master'
    }]
};

npm install -g comigoji-changelog
comigoji-changelog ./comigojiChangelog.js > Changelog.md

Note that this changelog tool does not choose by itself the point from which to write the changelog. If since parameter is not specified for each repo, then it will fetch all the commits in these repositories. As you can use a .js file as an input, you can perform any computations before generating a changelog, be they synchronous or not. An example that gets a latest tag's date from one repository and applies it to other ones:

// yourProject/comigojiChangelog.js
// This gets a datetime string of the latest tagged commit
const gitCommand = 'git log --max-count=1 --tags --simplify-by-decoration --pretty="format:%cI"';
const {exec} = require('child_process');

module.exports = new Promise((resolve, reject) => {
    // assuming that the current working directory is a git repo with relevant tags
    exec(gitCommand, function (err, stdout, stderr) {
        if (err) {
            reject(err);
            return;
        }
        if (stderr) {
            reject(new Error(stderr));
            return;
        }
        const since = new Date(stdout.trim());
        resolve({
            repos: [{
                since,
                repo: './',
                branch: 'develop'
            }, {
                since,
                repo: '/home/user/repo2',
                branch: 'master'
            }]
        });
    });
});

Defining your own categories

module.exports = {
    repos: [/* … */],
    categories: {
        // generic categories
        feature: {
            // should be a regexp or a string
            pattern: /^:(rainbow|sparkles):/,
            header: '### ✨ New Features'
        },
        improvement: {
            pattern: /^:(zap|wrench):/,
            header: '### ⚡️ General Improvements'
        },
        bug: {
            pattern: /^:bug:/,
            header: '### 🐛 Bug Fixes'
        },
        /* … */
        default: {
            // If you want strangely named commits to appear in the changelog, this section (`default`) should be present
            header: `### 👽 Misc`
        },
        ignore: {
            pattern: /^:(construction|doughnut|rocket|bookmark):/,
            skip: true // this makes specific commits to be ignored
        }
    }
};

Autocategories for doc sites, website updates, etc.

Certain repos may be configured so that their commits are automatically put into specific categories.

module.exports = {
    repos: [{
        repo: './docs',
        branch: 'master',
        forceCategory: 'docs',
        // Doc commits usually contain the 📝 symbol, which is already used in a header.
        // The line below will clean up these symbols.
        forceCategoryStrip: /^:(books|pencil|pencil2|memo):/
    }, {
        repo: './website',
        branch: 'master',
        // this repo's commit subjects will be written as is
        forceCategory: 'website'
    }],
    categories: {
        /* … */
        docs: {
            pattern: /^:(books|pencil|pencil2|memo):/,
            header: '### 📝 Docs'
        },
        website: {
            header: '### 🌐 Website'
        }
    }
};