Reset Stage

Automates the stage branch reset process documented in apps/docs/docs/04-engineering-practices/02-deployment/index.md.

When to use

• User says "reset stage", "rebuild stage", "stage is broken"
• User says "what if stage reset" or "dry run stage"
• Stage branch has conflicts preventing new PR merges
• Stage has drifted from main due to closed/stale PRs

Steps

1. Ensure the working tree is clean. If dirty, ask the user to stash or commit.

2. Run the script. Default is dry-run (safe, no changes):

   # Dry run — default, safe, no changes (never posts to Slack)
   ./tools/scripts/reset-stage.sh
   
   # Actual reset (destructive, prompts for confirmation).
   # Posts to Slack only if the run produced conflicts.
   ./tools/scripts/reset-stage.sh --apply
   
   # Hard opt-out: never post to Slack, even if conflicts occur.
   ./tools/scripts/reset-stage.sh --apply --no-slack
   

3. Show the full output to the user.

4. If --apply was used, remind the user:

   • Stage deploy workflows will trigger automatically on push
   • Slack was notified only if the run had auto-resolved or failed conflicts. Clean apply runs and dry runs stay silent — this is by design (ENG-3679) so the channel only fires when someone's on-stage PR may have actually been touched.
   • Any truly unresolvable PRs (very rare) need their authors to investigate

Trigger phrases

• "reset stage"
• "rebuild stage"
• "stage is broken"
• "what if stage reset"
• "dry run stage"

How conflict resolution works

The problem

Resetting stage from main and re-merging all "on stage" PRs used to replay the exact same conflicts that caused the reset in the first place. The reset didn't actually get you unstuck.

The solution: accept incoming changes (-X theirs)

The script uses a two-phase merge for each PR:

1. Try a clean merge — git merge origin/<branch> --no-ff
2. If that conflicts — abort, retry with git merge -X theirs
3. If -X theirs still fails (rare; e.g. modify/delete conflicts) — force-resolve remaining files by checking out the PR's version

-X theirs tells Git to resolve conflicted hunks by taking the incoming (PR branch) side. Non-conflicting changes from both sides are still merged normally via 3-way merge — it only overrides the conflicted parts.

Why this is safe

• Stage is ephemeral. It exists purely for integration testing and gets force-pushed on every reset. Nobody branches off it.
• PR branches are the source of truth. Each feature branch goes through proper code review before merging to main. Stage is just a preview.
• Worst case is a broken stage build. Which is the same outcome as a bad manual conflict resolution — and the fix is to run the reset again.
• The PR branch is never modified. Only the stage branch is affected.

Merge order

PRs are merged newest-first (highest PR number). When two PRs modify the same lines, the one merged second "wins" for those hunks. This is deterministic — same PR set + same order = same result.

Report categories

Category	Meaning
Clean merge	No conflicts at all
Auto-resolved	Had conflicts, resolved automatically via -X theirs
Failed	Could not be resolved even with force (very rare)
Missing branch	Remote branch no longer exists

Recovery

If stage is broken after a reset

Run the reset again. The script resets stage to main and force-pushes, so every reset starts completely fresh.

If an engineer's PR is causing problems on stage

1. The engineer's PR branch is never touched — only stage is affected.
2. The engineer rebases their branch against main and pushes.
3. The next stage reset picks up the fixed version automatically.
4. No manual merge conflict resolution is ever needed on the stage branch.

If you need to exclude a specific PR

Remove the "on stage" label from that PR before running the reset. The script only merges PRs that currently have the label.

Prerequisites

• gh CLI must be authenticated (gh auth login)
• Doppler must be authenticated for Slack notifications (doppler login)
  • Secrets: STAGE_RESET_SLACK_BOT_TOKEN, SLACK_ENGINEERING_CHANNEL_ID
  • Location: Doppler project core, config dev
• If Doppler is not authenticated, the script runs but skips Slack
• A confirmation prompt prevents accidental real resets (--apply)