fix(ubicloud): pack refuses a subdirectory git lists no files under instead of shipping an empty archive

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

scripts/ubicloud/ubi-runner.sh

@@ -1116,11 +1116,16 @@ cmd_down() {
 # subdirectory of a work tree ships the same file set without a .git: git's
 # local transport fetches only from a repository's root, and the whole
 # repository's .git would show the VM every file outside the subdirectory as
-# deleted (GST-935).
+# deleted (GST-935). A subdirectory git lists no files under (one the parent
+# ignores) is refused rather than shipped empty: cmd_run keys the run on the
+# local files and skips the tree check for a subdirectory, so an empty upload
+# would pass on content that never ran.
 cmd_pack() {
   local src tmp gitdir branch head entry
   src=$(cd "${1:-.}" && pwd)
   if git -C "$src" rev-parse --is-inside-work-tree >/dev/null 2>&1 && [ -n "$(git -C "$src" rev-parse --show-prefix)" ]; then
+    [ -n "$(git -C "$src" ls-files -co --exclude-standard | head -n 1)" ] \
+      || die "pack: git lists no files under $src (ignored by its checkout, or empty); nothing to ship"
     (
       cd "$src"
       export COPYFILE_DISABLE=1

test/ubicloud-runner.test.ts

@@ -395,6 +395,11 @@ test('pack ships a linked worktree with a self-contained .git on the checked-out
         expect(tree(vm)).toEqual(['./.gitignore', './a', './nested/b', './new']);
         expect(readFileSync(join(vm, 'a'), 'utf8')).toBe('edited\n');
       }
+      // A subdirectory the checkout ignores lists no files; pack refuses it instead of shipping an empty archive.
+      sh('echo scratch/ > .gitignore && mkdir -p scratch/job && echo s > scratch/job/f', join(d, 'repo'));
+      const ignored = Bun.spawnSync(['bash', join(DIR, 'ubi-runner.sh'), 'pack', 'scratch/job'], { cwd: join(d, 'repo'), timeout: 30_000 });
+      expect(ignored.exitCode).toBe(1);
+      expect(ignored.stderr.toString()).toContain('pack: git lists no files under');
     } finally { rmSync(d, { recursive: true, force: true }); }
   }, 60_000);