How to include git revision into angular-cli application?

The other answers were helpful, but I preferred a more simple, direct approach. Here's mine.

Run npm install git-describe --save-dev. Then add git-version.js to the root:

// This script runs operations *synchronously* which is normally not the best
// approach, but it keeps things simple, readable, and for now is good enough.

const { gitDescribeSync } = require('git-describe');
const { writeFileSync } = require('fs');

const gitInfo = gitDescribeSync();
const versionInfoJson = JSON.stringify(gitInfo, null, 2);

writeFileSync('git-version.json', versionInfoJson);

Optionally you can add /git-version.json to your .gitignore file.

Update your package.json to do something like this:

"scripts": {
  "build": "node git-version.js && ng build"
}

Then add version-info.ts to the root of your project:

export const versionInfo = (() => {
  try {
    // tslint:disable-next-line:no-var-requires
    return require('../../git-version.json');
  } catch {
    // In dev the file might not exist:
    return { tag: 'v0.0.0', hash: 'dev' };
  }
})();

And import the versionInfo in your app.component.ts or anywhere else you'd want to use it.

As suggested by @Yuri, I was able to solve this by using npm scripting.

1. Defined git.version.ts in the root of the angular-cli project:

import { Observable, combineLatest } from 'rxjs'

declare var require: any;
declare var process: any;

const fs = require('fs');
const exec = require('child_process').exec;

const revision = new Observable<string>(s => {
    exec('git rev-parse --short HEAD',
        (error: Error, stdout, stderr) => {
            if (error !== null) {
                console.log('git error: ' + error + stderr);
            }
            s.next(stdout.toString().trim());
            s.complete();
        });
});

const branch = new Observable<string>(s => {
    exec('git rev-parse --abbrev-ref HEAD',
        (error: Error, stdout, stderr) => {
            if (error !== null) {
                console.log('git error: ' + error + stderr);
            }
            s.next(stdout.toString().trim());
            s.complete();
        });
});

combineLatest(revision, branch)
    .subscribe(([revision, branch]) => {
        console.log(`version: '${process.env.npm_package_version}', revision: '${revision}', branch: '${branch}'`);

        const content = '// this file is automatically generated by git.version.ts script\n' +
            `export const versions = {version: '${process.env.npm_package_version}', revision: '${revision}', branch: '${branch}'};`;

        fs.writeFileSync(
            'src/environments/versions.ts',
            content,
            {encoding: 'utf8'}
        );
    });

2. Added pre-build hook in package.json:

"scripts": {
    "ng": "ng",
    ...
    "start": "ng serve --proxy proxy-config.json",
    "prebuild.prod": "ts-node -O \"{\\\"module\\\":\\\"commonjs\\\"}\" git.version.ts",
    "build.prod": "ng build -prod",
    ...
}

3. Use the generated src/environments/versions.ts in the application.

   UPDATE 10/2018: Here is the more-readable version of the script, rxjs-version-agnostic:

import { writeFileSync } from 'fs';
import { dedent } from 'tslint/lib/utils';
import { promisify } from 'util';
import * as child from 'child_process';
const exec = promisify(child.exec);

async function createVersionsFile(filename: string) {
  const revision = (await exec('git rev-parse --short HEAD')).stdout.toString().trim();
  const branch = (await exec('git rev-parse --abbrev-ref HEAD')).stdout.toString().trim();

  console.log(`version: '${process.env.npm_package_version}', revision: '${revision}', branch: '${branch}'`);

  const content = dedent`
      // this file is automatically generated by git.version.ts script
      export const versions = {
        version: '${process.env.npm_package_version}',
        revision: '${revision}',
        branch: '${branch}'
      };`;

  writeFileSync(filename, content, {encoding: 'utf8'});
}

createVersionsFile('src/environments/versions.ts');

Note, when using angular-cli v7.0.6, I also had to change script invocation in the package.json:

"scripts": {
    ...
    "prebuild.prod": "ts-node -O '{\"module\": \"commonjs\"}' git.version.ts",
    ...
}