Add version script

script/version

@@ -0,0 +1,49 @@
+#!/usr/bin/env node
+
+const fs = require('fs');
+const path = require('path');
+const {execFileSync} = require('child_process');
+
+const cliPath = path.join(__dirname, '..', 'cli');
+const npmPath = path.join(cliPath, 'npm');
+const cargoTomlPath = path.join(cliPath, 'Cargo.toml');
+
+const npmMetadata = require(path.join(npmPath, 'package.json'));
+const npmVersion = npmMetadata.version;
+
+const cargoMetadata = fs.readFileSync(cargoTomlPath, 'utf8')
+const cargoVersionMatch = cargoMetadata.match(/version = "([^"\n]+)"/);
+const cargoVersion = cargoVersionMatch[1];
+
+if (npmVersion !== cargoVersion) {
+  console.error(`NPM version ${npmVersion} does not match Cargo version ${cargoVersion}`);
+  process.exit(1);
+}
+
+if (process.argv[2]) {
+  // Check that working directory is clean
+  const diff = execFileSync(
+    'git',
+    ['diff', '--stat'],
+    {encoding: 'utf8'}
+  );
+  if (diff.length !== 0) {
+    console.error('There are uncommited changes.');
+    process.exit(1);
+  }
+
+  const newVersion = execFileSync(
+    'npm',
+    ['version', process.argv[2], '--git-tag-version=false'],
+    {cwd: npmPath, encoding: 'utf8'}
+  ).trim().replace(/^v/, '');
+  const newCargoVersionLine = cargoVersionMatch[0].replace(cargoVersion, newVersion);
+  const newCargoMetadata = cargoMetadata.replace(cargoVersionMatch[0], newCargoVersionLine);
+  fs.writeFileSync(cargoTomlPath, newCargoMetadata, 'utf8');
+  execFileSync('cargo', ['build'], {cwd: cliPath});
+  execFileSync('git', ['commit', '-a', '-m', newVersion]);
+  execFileSync('git', ['tag', newVersion]);
+  console.log(newVersion)
+} else {
+  console.log(npmVersion);
+}