feat: add function and task to get version of used dependency

Fixes #20

src/cli.ts

@@ -16,8 +16,10 @@ import {Api} from '@openstapps/gitlab-api';
 import {Logger} from '@openstapps/logger';
 import * as commander from 'commander';
 import {existsSync, readFileSync} from 'fs';
-import {join} from 'path';
+import {join, resolve} from 'path';
+import {cwd, stdout} from 'process';
 import {GITLAB_API_URL} from './configuration';
+import {getUsedVersionMajorMinor} from './tasks/get-used-version';
 import {remind} from './tasks/remind';
 import {tidy} from './tasks/tidy';
 import {unlabel} from './tasks/unlabel';
@@ -63,6 +65,17 @@ commander
     Logger.ok('Done!');
   });
 
+commander
+  .command('get-used-version <dependency> [path]')
+  .action(async (dependency, path) => {
+    let fallbackPath = cwd();
+    if (typeof path === 'string' && path.length > 0) {
+      fallbackPath = resolve(path);
+    }
+
+    stdout.write(await getUsedVersionMajorMinor(fallbackPath, dependency), process.exit);
+  });
+
 commander
   .parse(process.argv);