fix(ubicloud): pack and sync a subdirectory of a git checkout (GST-935)

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

scripts/ubicloud/ubi-runner.sh

@@ -1112,11 +1112,26 @@ cmd_down() {
 # options at the first operand and resolves -T names after a -C, so no single
 # tar command line works on both it and GNU tar (#3680). COPYFILE_DISABLE=1
 # keeps Apple's tar from adding ._* AppleDouble entries for files with
-# extended attributes, which the VM would see as untracked files.
+# extended attributes, which the VM would see as untracked files. A
+# 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).
 cmd_pack() {
   local src tmp gitdir branch head entry
   src=$(cd "${1:-.}" && pwd)
-  if git -C "$src" rev-parse --is-inside-work-tree >/dev/null 2>&1; then
+  if git -C "$src" rev-parse --is-inside-work-tree >/dev/null 2>&1 && [ -n "$(git -C "$src" rev-parse --show-prefix)" ]; then
+    (
+      cd "$src"
+      export COPYFILE_DISABLE=1
+      git ls-files -z -co --exclude-standard \
+        | while IFS= read -r -d '' f; do
+            if [ -e "$f" ] || [ -L "$f" ]; then printf '%s\0' "$f"; fi
+          done \
+        | tar --null -T - -cf - \
+        | gzip -c
+    )
+  elif git -C "$src" rev-parse --is-inside-work-tree >/dev/null 2>&1; then
     head=$(git -C "$src" rev-parse --verify -q HEAD) || die "pack: $src has no commits; the VM needs a HEAD to fingerprint"
     branch=$(git -C "$src" symbolic-ref -q --short HEAD || true)
     tmp=$(mktemp -d)

test/ubicloud-runner.test.ts

@@ -380,6 +380,24 @@ test('pack ships a linked worktree with a self-contained .git on the checked-out
     } finally { rmSync(d, { recursive: true, force: true }); }
   }, 60_000);
 
+  // Value: protects=sync and pack of a subdirectory of a git checkout (gstack-evals' launch.sh syncs quick/laneb/runner) ship that subdirectory's working files; fails_when=pack fetches refs from a path below the work tree's root, which git's local transport refuses, or ships the whole repository's .git so the VM sees every file outside the subdirectory as deleted; why_new=every pack test packs a work tree's root or a plain directory; seam=none
+  test('pack of a subdirectory of a checkout or a linked worktree ships its tracked, edited and untracked files without a .git', () => {
+    const d = mkdtempSync(join(tmpdir(), 'ubi-pack-subdir-'));
+    try {
+      const sh = (cmd: string, cwd: string) => { const r = Bun.spawnSync(['bash', '-c', cmd], { cwd, timeout: 30_000, env: { ...process.env, GIT_AUTHOR_NAME: 't', GIT_AUTHOR_EMAIL: 't@t', GIT_COMMITTER_NAME: 't', GIT_COMMITTER_EMAIL: 't@t' } }); expect(r.exitCode, `${cmd}\n${r.stderr.toString()}`).toBe(0); return r.stdout.toString(); };
+      sh('git init -q repo && cd repo && echo top > top && mkdir -p sub/nested && echo a > sub/a && echo b > sub/nested/b && echo g > sub/gone && echo "*.log" > sub/.gitignore && git add -A && git commit -qm one && git worktree add -q ../wt', d);
+      const tree = (dir: string) => sh('find . -type f | sort', dir).split('\n').filter(Boolean);
+      for (const checkout of ['repo', 'wt']) {
+        const sub = join(d, checkout, 'sub');
+        sh('echo edited > a && rm gone && echo n > new && echo x > x.log', sub);
+        const vm = join(d, `vm-${checkout}`);
+        sh(`mkdir ${JSON.stringify(vm)} && bash ${JSON.stringify(join(DIR, 'ubi-runner.sh'))} pack sub | tar -xzf - -C ${JSON.stringify(vm)}`, join(d, checkout));
+        expect(tree(vm)).toEqual(['./.gitignore', './a', './nested/b', './new']);
+        expect(readFileSync(join(vm, 'a'), 'utf8')).toBe('edited\n');
+      }
+    } finally { rmSync(d, { recursive: true, force: true }); }
+  }, 60_000);
+
   test('pack snapshots a plain checkout without reading its live .git: remotes resolve, a detached HEAD gets a branch, and git running beside it cannot fail the tar', () => {
     const d = mkdtempSync(join(tmpdir(), 'ubi-pack-live-'));
     try {