Add capture() to spawn, add rsync itemize parser

lib/spawn.js

@@ -4,17 +4,14 @@
 import { spawn } from 'child_process';
 
 /**
- * Spawn a process and stream its output.
+ * Spawn a process and stream its output to stdout/stderr.
  * @param {string} cmd
  * @param {string[]} args
- * @param {{ dryRun?: boolean, label?: string }} opts
+ * @param {{ dryRun?: boolean }} opts
  * @returns {Promise<void>}
  */
-export async function run(cmd, args, { dryRun = false, label } = {}) {
-  const display = [cmd, ...args].join(' ');
-  if (label) console.log(`[${label}] ${display}`);
-  else console.log(`$ ${display}`);
-
+export async function run(cmd, args, { dryRun = false } = {}) {
+  console.log(`$ ${[cmd, ...args].join(' ')}`);
   if (dryRun) return;
 
   return new Promise((resolve, reject) => {
@@ -26,3 +23,25 @@ export async function run(cmd, args, { dryRun = false, label } = {}) {
     });
   });
 }
+
+/**
+ * Spawn a process and capture stdout as a string.
+ * stderr is inherited (shown to user). Never used in dry-run context.
+ * @param {string} cmd
+ * @param {string[]} args
+ * @returns {Promise<string>}
+ */
+export async function capture(cmd, args) {
+  console.log(`$ ${[cmd, ...args].join(' ')}`);
+
+  return new Promise((resolve, reject) => {
+    const child = spawn(cmd, args, { stdio: ['inherit', 'pipe', 'inherit'] });
+    const chunks = [];
+    child.stdout.on('data', chunk => chunks.push(chunk));
+    child.on('error', reject);
+    child.on('close', code => {
+      if (code === 0) resolve(Buffer.concat(chunks).toString('utf8'));
+      else reject(new Error(`${cmd} exited with code ${code}`));
+    });
+  });
+}