feat(backend): skip getCommitHashForRefName for empty repos

Adds isRepoEmpty utility to git.ts and uses it in repoIndexManager to
avoid calling getCommitHashForRefName on repos with no commits, preventing
noisy debug log output for empty repositories.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: brendan-kellam

packages/backend/src/git.ts

@@ -415,6 +415,23 @@ export const getLatestCommitTimestamp = async ({
     }
 }
 
+/**
+ * Returns true if the git repository at the given path has no commits.
+ */
+export const isRepoEmpty = async ({
+    path,
+}: {
+    path: string,
+}): Promise<boolean> => {
+    const git = createGitClientForPath(path);
+    try {
+        const result = await git.raw(['log', '--all', '-1', '--format=%H']);
+        return result.trim() === '';
+    } catch {
+        return true;
+    }
+}
+
 /**
  * Writes or updates the commit-graph file for the repository.
  * This pre-computes commit metadata to speed up operations like

packages/backend/src/repoIndexManager.ts

@@ -8,7 +8,7 @@ import { Redis } from 'ioredis';
 import micromatch from 'micromatch';
 import Redlock, { ExecutionError } from 'redlock';
 import { INDEX_CACHE_DIR, WORKER_STOP_GRACEFUL_TIMEOUT_MS } from './constants.js';
-import { cloneRepository, fetchRepository, getBranches, getCommitHashForRefName, getLatestCommitTimestamp, getLocalDefaultBranch, getTags, isPathAValidGitRepoRoot, unsetGitConfig, upsertGitConfig } from './git.js';
+import { cloneRepository, fetchRepository, getBranches, getCommitHashForRefName, getLatestCommitTimestamp, getLocalDefaultBranch, getTags, isPathAValidGitRepoRoot, isRepoEmpty, unsetGitConfig, upsertGitConfig } from './git.js';
 import { captureEvent } from './posthog.js';
 import { PromClient } from './promClient.js';
 import { RepoWithConnections, Settings } from "./types.js";
@@ -531,7 +531,8 @@ export class RepoIndexManager {
 
             if (jobData.type === RepoIndexingJobType.INDEX) {
                 const { path: repoPath } = getRepoPath(jobData.repo);
-                const commitHash = await getCommitHashForRefName({
+                const isEmpty = await isRepoEmpty({ path: repoPath });
+                const commitHash = isEmpty ? undefined : await getCommitHashForRefName({
                     path: repoPath,
                     refName: 'HEAD',
                 });