added duration example

src/commands/duration.js

@@ -0,0 +1,16 @@
+// @flow
+
+import Command from 'cli-engine-command'
+import DurationFlag from '../flags/duration'
+
+export default class extends Command {
+  static topic = 'cli'
+  static command = 'duration'
+  static description = 'this is an example command showing duration parsing'
+  static flags = {duration: DurationFlag()}
+
+  async run () {
+    this.log('duration:')
+    this.inspect(this.flags.duration)
+  }
+}

src/flags/duration.js

@@ -0,0 +1,19 @@
+// @flow
+
+import type {Flag} from 'cli-engine-command'
+
+type Options = $Shape<Flag<Date>>
+
+export default function DurationFlag (options: Options = {}, env: typeof process.env = process.env): Flag<Date> {
+  const defaultOptions: Options = {
+    description: 'a duration',
+    parse: (input) => {
+      if (!input) {
+        if (options.required) throw new Error('No org specified')
+        return
+      }
+      return new Date(input)
+    }
+  }
+  return Object.assign(defaultOptions, options)
+}

src/index.js

@@ -4,5 +4,7 @@ export const topics = [
   {name: 'cli', description: 'example CLI engine topic'}
 ]
 
-import CLI from './commands/cli'
-export const commands = [CLI]
+export const commands = [
+  require('./commands/cli'),
+  require('./commands/duration')
+]