name: Require Linear issue

# Every INTERNAL PR must reference a Linear issue (e.g. COG-123) in its title or
# branch name — that is how Linear links a PR to a ticket. Since Linear does not
# gate merges, enforcement is a required GitHub status check: this job fails when a
# PR has no Linear key, and branch protection blocks the merge until it passes.
#
# Fork / external-contributor PRs are intentionally SKIPPED: they have no Linear
# access, and a skipped required check counts as passing, so this never blocks the
# community. Mark the `linear-issue-check` job as a required status check on
# `main` and `dev` in branch protection.

on:
  pull_request:
    # `synchronize` matters: a required check must re-run on the latest commit.
    types: [opened, edited, reopened, synchronize]

permissions:
  contents: read

jobs:
  linear-issue-check: # this job name is what you mark "required" in branch protection
    # Enforce for internal PRs only. Fork PRs (head repo != base repo) skip this job;
    # a skipped required check is treated as passing, so external PRs are not blocked.
    if: github.event.pull_request.head.repo.full_name == github.repository
    runs-on: ubuntu-latest
    steps:
      - name: PR title or branch must reference a Linear issue
        env:
          PR_TITLE: ${{ github.event.pull_request.title }}
          HEAD_REF: ${{ github.head_ref }}
        run: |
          # List ALL your Linear team prefixes — verify against Linear ▸ Settings ▸ Teams.
          KEYS='COG|SDK|CLO|COM|ENG'
          if echo "$PR_TITLE $HEAD_REF" | grep -Eiq "\b(${KEYS})-[0-9]+\b"; then
            echo "Linear issue reference found."
          else
            echo "::error::PR title or branch must reference a Linear issue, e.g. COG-123."
            exit 1
          fi