Add a dry run CLI to help debug

.env.example

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+LOCAL_GITHUB_ACCESS_TOKEN=XXXX

src/dependabot/util.ts

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+export function parseNwo (nwo: string): {owner: string; repo: string} {
+  const [owner, name] = nwo.split('/')
+
+  if (!owner || !name) {
+    throw new Error(`'${nwo}' does not appear to be a valid repository NWO`)
+  }
+
+  return { owner: owner, repo: name }
+}

src/dry-run.ts

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+/* eslint-disable no-console, @typescript-eslint/no-var-requires, no-unused-expressions */
+import * as github from '@actions/github'
+import { Context } from '@actions/github/lib/context'
+import * as dotenv from 'dotenv'
+import { Argv } from 'yargs'
+import { hideBin } from 'yargs/helpers'
+
+import { getMessage } from './dependabot/verified_commits'
+import { parse } from './dependabot/update_metadata'
+import { parseNwo } from './dependabot/util'
+
+async function check (args: any): Promise<void> {
+  try {
+    const githubToken = process.env.LOCAL_GITHUB_ACCESS_TOKEN
+
+    if (!githubToken) {
+      console.log('You must set LOCAL_GITHUB_ACCESS_TOKEN to perform dry runs.')
+      process.exit(1)
+    }
+
+    const repoDetails = parseNwo(args.nwo)
+    const actionContext = new Context()
+    // Convert the CLI args into a stubbed Webhook payload
+    actionContext.payload = {
+      pull_request: {
+        number: args.prNumber
+      },
+      repository: {
+        owner: {
+          login: repoDetails.owner
+        },
+        name: repoDetails.repo
+      }
+    }
+    // Bypass the actor check for purpose of a dry run
+    actionContext.actor = 'dependabot[bot]'
+
+    const githubClient = github.getOctokit(githubToken)
+
+    // Retries the commit message if the PR is from Dependabot
+    const commitMessage = await getMessage(githubClient, actionContext)
+
+    if (commitMessage) {
+      console.log('This appears to be a valid Dependabot Pull Request.')
+
+      const updatedDependencies = parse(commitMessage)
+
+      if (updatedDependencies.length > 0) {
+        console.log('Updated dependencies:')
+        console.log(JSON.stringify(updatedDependencies, undefined, 2))
+      } else {
+        console.log('No dependabot metadata found!')
+      }
+    } else {
+      console.log('This is not a Dependabot Pull Request.')
+      process.exit(1)
+    }
+  } catch (exception) {
+    console.log(exception.message)
+    process.exit(1)
+  }
+}
+
+dotenv.config()
+
+require('yargs')(hideBin(process.argv))
+  .command('check <nwo> <pr-number>', 'Perform a dry run on the given PR number of the NWO repo', (yargs) => {
+    yargs.positional('nwo', {
+      describe: 'The name with owner representation of a target repository, e.g. github/github',
+      type: 'string'
+    })
+    yargs.positional('pr-number', {
+      describe: 'The integer number of the target pull request to dry run',
+      type: 'number'
+    })
+    yargs.demandOption(['nwo', 'pr-number'])
+  }, (args: Argv) => {
+    check(args)
+  })
+  .demandCommand(1)
+  .help()
+  .argv