reviewer-bot: workflow_dispatch reads default-branch code for explore tools (set REVIEW_CONTENT_ROOT)

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#865 0 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
84/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Quiet
Tech stack
github-actions, python
Domain
ci-cd, security

Research direction

Start in reviewer-bot.yml and inspect the workflow_dispatch path alongside review_bot/run_review.py's _content_root() behavior. Verify how HEAD_SHA is obtained and how the separate checkout and REVIEW_CONTENT_ROOT should be wired without changing the trusted primary checkout. Done means manual dispatch explores the PR head while pull_request behavior remains unchanged.

Written by the indexing model from the issue text.

Description

Follow-up from PR #862 review (thread on reviewer-bot.yml).

Problem

On the workflow_dispatch (manual) trigger, reviewer-bot.yml does a single actions/checkout with no ref:, which resolves to the default branch — not the PR being reviewed. The PR head is resolved separately (HEAD_SHA = gh pr view ... --json headRefOid).

Result:

  • The review diff and comment anchors are correct — the engine fetches them from the GitHub compare API keyed on HEAD_SHA (repos/{repo}/compare/...), independent of the checkout.
  • But the agent's explore tools (read_paths / grep) read from the engine's _content_root(), which falls back to the primary checkout (= default branch on dispatch) when REVIEW_CONTENT_ROOT is unset. So on manual dispatch, the agent explores default-branch code, not the PR head.

The automatic pull_request trigger (the normal case) is unaffected — its checkout already is the PR merge ref.

Why the engine expects this

Per reviewer_bot/run_review.py _content_root(), workflow_dispatch is meant to check the PR head into a separate directory and export its path as REVIEW_CONTENT_ROOT, while engine code keeps running from the trusted default-branch checkout. This is a deliberate security boundary: dispatch is exempt from the fork guard, so the PR's own code must not run/read from the primary checkout dir.

Fix

On the dispatch path, add a second checkout of HEAD_SHA into a separate dir and export REVIEW_CONTENT_ROOT pointing at it (mirroring the engine's documented pattern).

Severity

Low — only manual dispatch is affected, and only the explore-tool reads (diff/anchors are always correct). Deferred from #862 as a follow-up.

Dominant language
Python
Stars
233
Forks
152
Avg merge
21h 5m
Merged PRs (30d)
10

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