fix(review): detect remote default branch via ls-remote when origin/HEAD is unset

getDefaultBranch relied on `symbolic-ref refs/remotes/origin/HEAD` to
prefer the upstream ref over a potentially stale local copy. But
origin/HEAD is commonly unset — worktrees, manual remote additions,
and certain git operations can leave it missing. When it was absent,
the code skipped straight to local `main`/`master`, silently losing
the upstream-preference behavior for any user without origin/HEAD.

Adds a second-order fallback: `git ls-remote --symref origin HEAD`
queries the remote directly for its default branch. Works for any
branch name (develop, trunk, etc.) — no hardcoded guesses. Uses a
3-second timeout so offline users aren't blocked; on failure it falls
through to the existing local main/master path.

To support the timeout, `ReviewGitRuntime.runGit` gains an optional
`timeoutMs` param. Bun's implementation kills the process via
setTimeout + proc.kill(). Pi's uses spawnSync's native `timeout`
option. Both treat timeout as a non-zero exit (graceful fallback).

For provenance purposes, this commit was AI assisted.

Author: backnotprop

apps/pi-extension/server/serverReview.ts

@@ -106,11 +106,12 @@ export interface ReviewServerResult {
 export const reviewRuntime: ReviewGitRuntime = {
 	async runGit(
 		args: string[],
-		options?: { cwd?: string },
+		options?: { cwd?: string; timeoutMs?: number },
 	): Promise<GitCommandResult> {
 		const result = spawnSync("git", args, {
 			cwd: options?.cwd,
 			encoding: "utf-8",
+			...(options?.timeoutMs ? { timeout: options.timeoutMs } : {}),
 		});
 		return {
 			stdout: result.stdout ?? "",

packages/server/git.ts

@@ -36,20 +36,27 @@ export type {
 
 async function runGit(
   args: string[],
-  options?: { cwd?: string },
+  options?: { cwd?: string; timeoutMs?: number },
 ): Promise<GitCommandResult> {
   const proc = Bun.spawn(["git", ...args], {
     cwd: options?.cwd,
     stdout: "pipe",
     stderr: "pipe",
   });
 
+  let timer: ReturnType<typeof setTimeout> | undefined;
+  if (options?.timeoutMs) {
+    timer = setTimeout(() => proc.kill(), options.timeoutMs);
+  }
+
   const [stdout, stderr, exitCode] = await Promise.all([
     new Response(proc.stdout).text(),
     new Response(proc.stderr).text(),
     proc.exited,
   ]);
 
+  if (timer) clearTimeout(timer);
+
   return { stdout, stderr, exitCode };
 }
 

packages/shared/review-core.ts

@@ -59,7 +59,7 @@ export interface GitCommandResult {
 export interface ReviewGitRuntime {
   runGit: (
     args: string[],
-    options?: { cwd?: string },
+    options?: { cwd?: string; timeoutMs?: number },
   ) => Promise<GitCommandResult>;
   readTextFile: (path: string) => Promise<string | null>;
 }
@@ -102,6 +102,31 @@ export async function getDefaultBranch(
     }
   }
 
+  // origin/HEAD wasn't set or pointed at an unfetched ref. Query the remote
+  // directly for its default branch — works for any branch name (develop,
+  // trunk, etc.), not just main/master. Best-effort with a 3s timeout so
+  // offline users aren't blocked. Parses the `ref: refs/heads/<name>` line
+  // from `git ls-remote --symref origin HEAD`.
+  try {
+    const lsRemote = await runtime.runGit(
+      ["ls-remote", "--symref", "origin", "HEAD"],
+      { cwd, timeoutMs: 5000 },
+    );
+    if (lsRemote.exitCode === 0) {
+      const match = lsRemote.stdout.match(/^ref:\s+refs\/heads\/(\S+)\s+HEAD/m);
+      if (match) {
+        const remoteBranch = `origin/${match[1]}`;
+        const refExists = await runtime.runGit(
+          ["show-ref", "--verify", "--quiet", `refs/remotes/${remoteBranch}`],
+          { cwd },
+        );
+        if (refExists.exitCode === 0) return remoteBranch;
+      }
+    }
+  } catch {
+    // Network unavailable, auth failure, or timeout — fall through.
+  }
+
   const mainBranch = await runtime.runGit(
     ["show-ref", "--verify", "refs/heads/main"],
     { cwd },