Add script to backfill duplicate comments for old issues

Creates a script that identifies old issues without duplicate detection comments and triggers the existing claude-dedupe-issues workflow for each one. This helps ensure historical issues get proper duplicate detection coverage.

Features:
- Scans issues from configurable time period (default 30 days)
- Skips issues that already have duplicate detection comments
- Triggers existing workflow instead of duplicating logic
- Includes dry-run mode and rate limiting for safety

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/backfill-duplicate-comments.ts

@@ -0,0 +1,198 @@
+#!/usr/bin/env bun
+
+declare global {
+  var process: {
+    env: Record<string, string | undefined>;
+  };
+}
+
+interface GitHubIssue {
+  number: number;
+  title: string;
+  state: string;
+  state_reason?: string;
+  user: { id: number };
+  created_at: string;
+  closed_at?: string;
+}
+
+interface GitHubComment {
+  id: number;
+  body: string;
+  created_at: string;
+  user: { type: string; id: number };
+}
+
+async function githubRequest<T>(endpoint: string, token: string, method: string = 'GET', body?: any): Promise<T> {
+  const response = await fetch(`https://api.github.com${endpoint}`, {
+    method,
+    headers: {
+      Authorization: `Bearer ${token}`,
+      Accept: "application/vnd.github.v3+json",
+      "User-Agent": "backfill-duplicate-comments-script",
+      ...(body && { "Content-Type": "application/json" }),
+    },
+    ...(body && { body: JSON.stringify(body) }),
+  });
+
+  if (!response.ok) {
+    throw new Error(
+      `GitHub API request failed: ${response.status} ${response.statusText}`
+    );
+  }
+
+  return response.json();
+}
+
+async function triggerDedupeWorkflow(
+  owner: string,
+  repo: string,
+  issueNumber: number,
+  token: string,
+  dryRun: boolean = true
+): Promise<void> {
+  if (dryRun) {
+    console.log(`[DRY RUN] Would trigger dedupe workflow for issue #${issueNumber}`);
+    return;
+  }
+
+  await githubRequest(
+    `/repos/${owner}/${repo}/actions/workflows/claude-dedupe-issues.yml/dispatches`,
+    token,
+    'POST',
+    {
+      ref: 'main',
+      inputs: {
+        issue_number: issueNumber.toString()
+      }
+    }
+  );
+}
+
+async function backfillDuplicateComments(): Promise<void> {
+  console.log("[DEBUG] Starting backfill duplicate comments script");
+
+  const token = process.env.GITHUB_TOKEN;
+  if (!token) {
+    throw new Error(`GITHUB_TOKEN environment variable is required
+
+Usage:
+  GITHUB_TOKEN=your_token bun run scripts/backfill-duplicate-comments.ts
+
+Environment Variables:
+  GITHUB_TOKEN - GitHub personal access token with repo and actions permissions (required)
+  DRY_RUN - Set to "false" to actually trigger workflows (default: true for safety)
+  DAYS_BACK - How many days back to look for old issues (default: 90)`);
+  }
+  console.log("[DEBUG] GitHub token found");
+
+  const owner = "anthropics";
+  const repo = "claude-code";
+  const dryRun = process.env.DRY_RUN !== "false";
+  const daysBack = parseInt(process.env.DAYS_BACK || "90", 10);
+  
+  console.log(`[DEBUG] Repository: ${owner}/${repo}`);
+  console.log(`[DEBUG] Dry run mode: ${dryRun}`);
+  console.log(`[DEBUG] Looking back ${daysBack} days`);
+
+  const cutoffDate = new Date();
+  cutoffDate.setDate(cutoffDate.getDate() - daysBack);
+
+  console.log(`[DEBUG] Fetching issues created since ${cutoffDate.toISOString()}...`);
+  const allIssues: GitHubIssue[] = [];
+  let page = 1;
+  const perPage = 100;
+  
+  while (true) {
+    const pageIssues: GitHubIssue[] = await githubRequest(
+      `/repos/${owner}/${repo}/issues?state=all&per_page=${perPage}&page=${page}&since=${cutoffDate.toISOString()}`,
+      token
+    );
+    
+    if (pageIssues.length === 0) break;
+    
+    allIssues.push(...pageIssues);
+    page++;
+    
+    // Safety limit to avoid infinite loops
+    if (page > 100) {
+      console.log("[DEBUG] Reached page limit, stopping pagination");
+      break;
+    }
+  }
+  
+  console.log(`[DEBUG] Found ${allIssues.length} issues from the last ${daysBack} days`);
+
+  let processedCount = 0;
+  let candidateCount = 0;
+  let triggeredCount = 0;
+
+  for (const issue of allIssues) {
+    processedCount++;
+    console.log(
+      `[DEBUG] Processing issue #${issue.number} (${processedCount}/${allIssues.length}): ${issue.title}`
+    );
+
+    console.log(`[DEBUG] Fetching comments for issue #${issue.number}...`);
+    const comments: GitHubComment[] = await githubRequest(
+      `/repos/${owner}/${repo}/issues/${issue.number}/comments`,
+      token
+    );
+    console.log(
+      `[DEBUG] Issue #${issue.number} has ${comments.length} comments`
+    );
+
+    // Look for existing duplicate detection comments (from the dedupe bot)
+    const dupeDetectionComments = comments.filter(
+      (comment) =>
+        comment.body.includes("Found") &&
+        comment.body.includes("possible duplicate") &&
+        comment.user.type === "Bot"
+    );
+
+    console.log(
+      `[DEBUG] Issue #${issue.number} has ${dupeDetectionComments.length} duplicate detection comments`
+    );
+
+    // Skip if there's already a duplicate detection comment
+    if (dupeDetectionComments.length > 0) {
+      console.log(
+        `[DEBUG] Issue #${issue.number} already has duplicate detection comment, skipping`
+      );
+      continue;
+    }
+
+    candidateCount++;
+    const issueUrl = `https://github.com/${owner}/${repo}/issues/${issue.number}`;
+    
+    try {
+      console.log(
+        `[INFO] ${dryRun ? '[DRY RUN] ' : ''}Triggering dedupe workflow for issue #${issue.number}: ${issueUrl}`
+      );
+      await triggerDedupeWorkflow(owner, repo, issue.number, token, dryRun);
+      
+      if (!dryRun) {
+        console.log(
+          `[SUCCESS] Successfully triggered dedupe workflow for issue #${issue.number}`
+        );
+      }
+      triggeredCount++;
+    } catch (error) {
+      console.error(
+        `[ERROR] Failed to trigger workflow for issue #${issue.number}: ${error}`
+      );
+    }
+
+    // Add a delay between workflow triggers to avoid overwhelming the system
+    await new Promise(resolve => setTimeout(resolve, 1000));
+  }
+
+  console.log(
+    `[DEBUG] Script completed. Processed ${processedCount} issues, found ${candidateCount} candidates without duplicate comments, ${dryRun ? 'would trigger' : 'triggered'} ${triggeredCount} workflows`
+  );
+}
+
+backfillDuplicateComments().catch(console.error);
+
+// Make it a module
+export {};