fix(gsd): deduplicate resolveGitHeadPath function (#1015)

Move resolveGitHeadPath() and nudgeGitBranchCache() to worktree.ts as
the canonical shared location. Both auto-worktree.ts and
worktree-command.ts now import from worktree.ts instead of defining
their own copies.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/resources/extensions/gsd/auto-worktree.ts

@@ -6,8 +6,8 @@
  * manages create, enter, detect, and teardown for auto-mode worktrees.
  */
 
-import { existsSync, cpSync, readFileSync, writeFileSync, readdirSync, mkdirSync, realpathSync, utimesSync, unlinkSync } from "node:fs";
-import { isAbsolute, join, resolve } from "node:path";
+import { existsSync, cpSync, readFileSync, writeFileSync, readdirSync, mkdirSync, realpathSync, unlinkSync } from "node:fs";
+import { isAbsolute, join } from "node:path";
 import { GSDError, GSD_IO_ERROR, GSD_GIT_ERROR } from "./errors.js";
 import { copyWorktreeDb, reconcileWorktreeDb, isDbAvailable } from "./gsd-db.js";
 import { execSync, execFileSync } from "node:child_process";
@@ -16,7 +16,7 @@ import {
   removeWorktree,
   worktreePath,
 } from "./worktree-manager.js";
-import { detectWorktreeName } from "./worktree.js";
+import { detectWorktreeName, resolveGitHeadPath, nudgeGitBranchCache } from "./worktree.js";
 import {
   MergeConflictError,
   readIntegrationBranch,
@@ -43,41 +43,6 @@ import {
 /** Original project root before chdir into auto-worktree. */
 let originalBase: string | null = null;
 
-// ─── Git Helpers (local, mirrors worktree-command.ts pattern) ──────────────
-
-function resolveGitHeadPath(dir: string): string | null {
-  const gitPath = join(dir, ".git");
-  if (!existsSync(gitPath)) return null;
-  try {
-    const content = readFileSync(gitPath, "utf8").trim();
-    if (content.startsWith("gitdir: ")) {
-      const gitDir = resolve(dir, content.slice(8));
-      const headPath = join(gitDir, "HEAD");
-      return existsSync(headPath) ? headPath : null;
-    }
-    const headPath = join(dir, ".git", "HEAD");
-    return existsSync(headPath) ? headPath : null;
-  } catch {
-    return null;
-  }
-}
-
-/**
- * Nudge pi's FooterDataProvider to re-read the git branch after chdir.
- * Touches HEAD in both old and new cwd to fire the fs watcher.
- */
-function nudgeGitBranchCache(previousCwd: string): void {
-  const now = new Date();
-  for (const dir of [previousCwd, process.cwd()]) {
-    try {
-      const headPath = resolveGitHeadPath(dir);
-      if (headPath) utimesSync(headPath, now, now);
-    } catch {
-      // Best-effort
-    }
-  }
-}
-
 // ─── Worktree Post-Create Hook (#597) ────────────────────────────────────────
 
 /**

src/resources/extensions/gsd/worktree-command.ts

@@ -12,7 +12,7 @@
 
 import type { ExtensionAPI, ExtensionCommandContext } from "@gsd/pi-coding-agent";
 import { loadPrompt } from "./prompt-loader.js";
-import { autoCommitCurrentBranch, getMainBranch } from "./worktree.js";
+import { autoCommitCurrentBranch, getMainBranch, resolveGitHeadPath, nudgeGitBranchCache } from "./worktree.js";
 import { runWorktreePostCreateHook } from "./auto-worktree.js";
 import { showConfirm } from "../shared/confirm-ui.js";
 import { gsdRoot, milestonesDir } from "./paths.js";
@@ -31,9 +31,9 @@ import {
 } from "./worktree-manager.js";
 import { inferCommitType } from "./git-service.js";
 import type { FileLineStat } from "./worktree-manager.js";
-import { existsSync, realpathSync, readFileSync, readdirSync, rmSync, unlinkSync, utimesSync } from "node:fs";
+import { existsSync, realpathSync, readdirSync, rmSync, unlinkSync } from "node:fs";
 import { nativeMergeAbort } from "./native-git-bridge.js";
-import { join, resolve, sep } from "node:path";
+import { join, sep } from "node:path";
 
 /**
  * Tracks the original project root so we can switch back.
@@ -46,52 +46,6 @@ export function getWorktreeOriginalCwd(): string | null {
   return originalCwd;
 }
 
-/**
- * Resolve the git HEAD file path for a given directory.
- * Handles both normal repos (.git is a directory) and worktrees (.git is a file).
- */
-function resolveGitHeadPath(dir: string): string | null {
-  const gitPath = join(dir, ".git");
-  if (!existsSync(gitPath)) return null;
-
-  try {
-    const content = readFileSync(gitPath, "utf8").trim();
-    if (content.startsWith("gitdir: ")) {
-      // Worktree — .git is a file pointing to the real gitdir
-      const gitDir = resolve(dir, content.slice(8));
-      const headPath = join(gitDir, "HEAD");
-      return existsSync(headPath) ? headPath : null;
-    }
-    // Normal repo — .git is a directory
-    const headPath = join(dir, ".git", "HEAD");
-    return existsSync(headPath) ? headPath : null;
-  } catch {
-    return null;
-  }
-}
-
-/**
- * Nudge pi's FooterDataProvider to re-read the git branch.
- *
- * The footer caches the branch and watches a single .git dir for changes.
- * After process.chdir() into a worktree (or back), the watcher is stale —
- * it's still watching the old git dir. We touch HEAD in both the old and
- * new git dirs to ensure the watcher fires regardless of which one it's
- * monitoring. This clears cachedBranch; the next getGitBranch() call uses
- * the new process.cwd() and picks up the correct branch.
- */
-function nudgeGitBranchCache(previousCwd: string): void {
-  const now = new Date();
-  for (const dir of [previousCwd, process.cwd()]) {
-    try {
-      const headPath = resolveGitHeadPath(dir);
-      if (headPath) utimesSync(headPath, now, now);
-    } catch {
-      // Best-effort — branch display may be stale
-    }
-  }
-}
-
 /** Get the name of the active worktree, or null if not in one. */
 export function getActiveWorktreeName(): string | null {
   if (!originalCwd) return null;

src/resources/extensions/gsd/worktree.ts

@@ -12,7 +12,8 @@
  * SLICE_BRANCH_RE) remain for backwards compatibility with legacy branches.
  */
 
-import { sep } from "node:path";
+import { existsSync, readFileSync, utimesSync } from "node:fs";
+import { join, resolve, sep } from "node:path";
 
 import { GitServiceImpl, writeIntegrationBranch, type TaskCommitContext } from "./git-service.js";
 import { loadEffectiveGSDPreferences } from "./preferences.js";
@@ -177,4 +178,43 @@ export function autoCommitCurrentBranch(
   return getService(basePath).autoCommit(unitType, unitId, [], taskContext);
 }
 
+// ─── Git HEAD Resolution ────────────────────────────────────────────────────
 
+/**
+ * Resolve the git HEAD file path for a given directory.
+ * Handles both normal repos (.git is a directory) and worktrees (.git is a file
+ * containing a `gitdir:` pointer to the real gitdir).
+ */
+export function resolveGitHeadPath(dir: string): string | null {
+  const gitPath = join(dir, ".git");
+  if (!existsSync(gitPath)) return null;
+
+  try {
+    const content = readFileSync(gitPath, "utf8").trim();
+    if (content.startsWith("gitdir: ")) {
+      const gitDir = resolve(dir, content.slice(8));
+      const headPath = join(gitDir, "HEAD");
+      return existsSync(headPath) ? headPath : null;
+    }
+    const headPath = join(dir, ".git", "HEAD");
+    return existsSync(headPath) ? headPath : null;
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Nudge pi's FooterDataProvider to re-read the git branch after chdir.
+ * Touches HEAD in both old and new cwd to fire the fs watcher.
+ */
+export function nudgeGitBranchCache(previousCwd: string): void {
+  const now = new Date();
+  for (const dir of [previousCwd, process.cwd()]) {
+    try {
+      const headPath = resolveGitHeadPath(dir);
+      if (headPath) utimesSync(headPath, now, now);
+    } catch {
+      // Best-effort
+    }
+  }
+}