chore: ensure branch push works for lts even if first time

Author: runspired

release/core/promote/index.ts

@@ -22,6 +22,7 @@ export async function promoteToLTS(args: string[]) {
   const versionsToPromote = getPublicPackageVersions(packages);
 
   await updateTags(config.full, versionsToPromote);
+
   if (config.full.get('upstream') && !config.full.get('dry_run')) {
     try {
       await pushLTSTagToRemoteBranch(gitTag, true);

release/utils/git.ts

@@ -181,7 +181,12 @@ export async function getAllPackagesForGitTag(tag: GIT_TAG): Promise<Map<string,
 export async function pushLTSTagToRemoteBranch(tag: GIT_TAG, force?: boolean): Promise<void> {
   const sha = await exec({ cmd: `git rev-list -n 1 ${tag}` });
   const branch = npmDistTagForChannelAndVersion('lts-prev', tag.slice(1) as SEMVER_VERSION);
-  const oldSha = await exec({ cmd: `git rev-list -n 1 refs/heads/${branch}` });
+  let oldSha = '<none>';
+  try {
+    oldSha = await exec({ cmd: `git rev-list -n 1 refs/heads/${branch}` });
+  } catch {
+    // no-op, branch does not exist
+  }
   let cmd = `git push origin refs/tags/${tag}:refs/heads/${branch}`;
   if (force) cmd += ' -f';
   await exec({ cmd });