feat: add git node staging command

Add a new `git node staging` command that automates cherry-picking
commits into staging branches.

It works by cherry-picking all commits that have no conflicts and
skipping any commits that have conflicts while automating the sending
of GitHub PR interactions to request backport for these commits,
sending a message to the original PR and properly labelling it.

Usage:

Fetches a commit list using `branch-diff` and automatically
cherry-picks / skips commits based on whether or not they land
cleanly:

  git node staging

Sets a custom reporter at the end of the automated operation:

  git node staging --reporter=markdown

Limits to 10 the number of commits to be cherry-picked:

  git node staging --pagination=10

Defines the release line (usually this can be inferred from the
ncu.branch value os it should not be required most of the time):

  git node staging --releaseLine=22

Automates the backport request message, this won't run any of the
`branch-diff` or cherry-pick routines. Useful for when you removed
a faulty commit from the branch and want to signal to PR author and
collaborators that commit now needs backporting, just use its PR#:

  git node staging --backport=12345

More:

The automate cherry-pick logic also includes local persistency of
the ongoing commit list, in case a fatal error happens during the
command execution, it's possible to resume after cleaning up the
git repo state by running `git node staging` again.

components/git/staging.js

@@ -0,0 +1,67 @@
+import CLI from '../../lib/cli.js';
+import { runPromise } from '../../lib/run.js';
+import { Staging } from '../../lib/staging.js';
+
+export const command = 'staging';
+export const describe = 'Automatic port commits to a release line branch';
+
+const stagingOptions = {
+  backport: {
+    describe: 'The PR ID / number to backport, skip staging commits',
+    type: 'number'
+  },
+  paginate: {
+    describe: 'Sets a maximum number of commits to port',
+    type: 'number'
+  },
+  skipGH: {
+    describe: 'Skip `gh` cli actions. Will not comment / label GitHub PRs',
+    type: 'boolean'
+  },
+  releaseLine: {
+    describe: 'The major version of the target release',
+    type: 'number'
+  },
+  reporter: {
+    describe: 'The reporter to use for the output',
+    type: 'string',
+    default: 'json'
+  }
+};
+
+export function builder(yargs) {
+  return yargs
+    .options(stagingOptions)
+    .example('git node staging --releaseLine=23',
+      'Port commits to the v1.x-staging branch');
+}
+
+export function handler(argv) {
+  const logStream = process.stdout.isTTY ? process.stdout : process.stderr;
+  const cli = new CLI(logStream);
+  const dir = process.cwd();
+
+  return runPromise(main(argv, cli, dir)).catch((err) => {
+    if (cli.spinner.enabled) {
+      cli.spinner.fail();
+    }
+    throw err;
+  });
+}
+
+async function main(argv, cli, dir) {
+  const { backport, paginate, releaseLine, reporter, skipGH } = argv;
+  const staging = new Staging({
+    cli,
+    dir,
+    paginate,
+    skipGH,
+    releaseLine,
+    reporter
+  });
+  if (backport) {
+    await staging.requestBackport(backport);
+  } else {
+    await staging.run();
+  }
+}

lib/prepare_release.js

@@ -523,12 +523,24 @@ export default class ReleasePreparation extends Session {
     const { newVersion } = this;
     const proposalBranch = `v${newVersion}-proposal`;
 
-    await runAsync('git', [
-      'checkout',
-      '-b',
-      proposalBranch,
-      base
-    ]);
+    try {
+      await forceRunAsync('git', [
+        'checkout',
+        '-b',
+        proposalBranch,
+        base
+      ], { captureStdout: true, captureStderr: true, ignoreFailures: false });
+    } catch (err) {
+      const branchExistsRE = /fatal: a branch named '.*' already exists/i;
+      if (branchExistsRE.test(err.stderr)) {
+        await runAsync('git', [
+          'checkout',
+          proposalBranch
+        ]);
+      } else {
+        throw err;
+      }
+    }
     return proposalBranch;
   }