From daeec2c0178ad103f64a9b062ddbbd7b81f63097 Mon Sep 17 00:00:00 2001
From: Garry Tan <garrytan@gmail.com>
Date: Fri, 14 Aug 2026 21:00:46 -0700
Subject: [PATCH] =?UTF-8?q?fix(slug):=20terminate=20the=20marker=20walk-up?=
 =?UTF-8?q?=20on=20dirname's=20fixed=20point=20=E2=80=94=20hung=20every=20?=
 =?UTF-8?q?bin=20on=20Windows?=
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Under git-bash on Windows a mixed-form path walks C:/Users -> C: -> . -> .
forever: dirname's fixed point there is never "/", so the walk-up loop spun
and every bin that evals gstack-slug (learnings-log first among them) hung
until spawn timeout. Caught by windows-free-tests CI on the wave PR. Break
on the fixed point itself with a depth cap for exotic forms; regression
tests drive the extracted function with hostile path shapes under a hard
timeout.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 bin/gstack-slug                      | 12 ++++++++++--
 test/gstack-slug-cwd-walk-up.test.ts | 20 ++++++++++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/bin/gstack-slug b/bin/gstack-slug
index 12c5b4643..e9b2aaf02 100755
--- a/bin/gstack-slug
+++ b/bin/gstack-slug
@@ -68,7 +68,12 @@ _outermost_project_root() {
   local dir="$1"
   local outermost_strong=""
   local outermost_weak=""
-  while [[ -n "$dir" && "$dir" != "/" ]]; do
+  local parent="" depth=0
+  # Terminate on dirname's FIXED POINT, not on a literal "/": under git-bash
+  # on Windows a mixed-form path walks C:/Users -> C: -> . -> . forever, which
+  # hung every bin that evals gstack-slug (caught by windows-free-tests CI).
+  # The depth cap is belt-and-braces for exotic path forms (UNC, //server).
+  while [[ -n "$dir" && "$dir" != "/" && $depth -lt 64 ]]; do
     if [[ -e "$dir/.git" \
        || -f "$dir/.project.yaml" \
        || -f "$dir/package.json" \
@@ -84,7 +89,10 @@ _outermost_project_root() {
          || -f "$dir/LICENSE.md" ]]; then
       outermost_weak="$dir"
     fi
-    dir=$(dirname "$dir")
+    parent=$(dirname "$dir")
+    [[ "$parent" == "$dir" ]] && break # dirname fixed point (C:/, ., //srv)
+    dir="$parent"
+    depth=$((depth + 1))
   done
   # Strong markers win over weak; either wins over nothing.
   if [[ -n "$outermost_strong" ]]; then
diff --git a/test/gstack-slug-cwd-walk-up.test.ts b/test/gstack-slug-cwd-walk-up.test.ts
index dac5cd919..96db5e303 100644
--- a/test/gstack-slug-cwd-walk-up.test.ts
+++ b/test/gstack-slug-cwd-walk-up.test.ts
@@ -289,3 +289,23 @@ describe('gstack-slug — outermost project-root resolution', () => {
     expect(slug).toBe('custom-override');
   });
 });
+
+describe('_outermost_project_root termination (windows-free-tests regression)', () => {
+  // Under git-bash on Windows a mixed-form path walks C:/Users -> C: -> . -> .
+  // forever: dirname's fixed point there is never "/". The loop must break on
+  // the fixed point itself. Extract the function and drive it with hostile
+  // path forms under a hard timeout — a hang fails the spawn, not the suite.
+  const script = fs.readFileSync(path.join(ROOT, 'bin', 'gstack-slug'), 'utf-8');
+  const fnMatch = script.match(/_outermost_project_root\(\) \{[\s\S]*?\n\}/);
+
+  test.each(['C:/Users/nobody/project', '.', '//server/share/dir'])(
+    'terminates on hostile path form: %s',
+    (hostile) => {
+      expect(fnMatch).not.toBeNull();
+      const r = Bun.spawnSync(['bash', '-c', `${fnMatch![0]}\n_outermost_project_root "$1"; echo TERMINATED`, '_', hostile], {
+        timeout: 5000,
+      });
+      expect(r.stdout.toString()).toContain('TERMINATED');
+    },
+  );
+});