[liuchao-001]

Part of #29.

Summary

Managed Git sources downloaded far more than the selected tree:

• The repository cache was a full git clone --bare. For first-tree-ai/opentag (tree at docs) this is 76 MB and 51 s.
• Cone-mode sparse snapshots also materialized every file at the repository root.

This change:

• Clones the cache as a treeless partial clone (--filter=tree:0). It stores commits only; directory trees and file contents are downloaded when a snapshot or write worktree checks them out. Later fetches inherit the filter via remote.origin.partialclonefilter.
• Uses non-cone sparse checkout with one anchored, escaped literal pattern (/<subtree>/) for snapshots and write worktrees, so only the selected subtree is materialized. Commits and publishing keep a full index and preserve outside paths.
• Tests against a filtering remote: only the selected subtree is downloaded; commit, publish, rejected push (WRITE_OUTDATED, session preserved), and a fresh retry all work through a treeless cache.
• Updates docs/specification.md.

Measurements (real first-tree-ai/opentag, docs, one Local Computer)

Cache	Clone	Size
full bare	51 s	76 MB
blob:none	6–24 s	12 MB
tree:0	2.5 s	2.3 MB

With a warm treeless cache: a fetch is about 1.2 s per repository; checking out a new commit of docs is about 3 s.

Validation

pnpm check, pnpm typecheck, pnpm test (118 tests), pnpm check:package pass.

Trade-offs

• sync --offline never fetches refs, but creating a snapshot whose trees or contents are not cached needs the remote.
• Existing full caches are left as-is; they shrink only if removed and re-synced.

🤖 Generated with Claude Code

[yuezengwu]

The treeless-cache and literal sparse-checkout behavior passed the full118-test suite, typecheck and repository check. One reproducible test-isolation defect remains: the object-presence assertions perform implicit external promisor fetches instead of staying local. Details are inline.

[yuezengwu]

Re-reviewed f89dc02 against current main2e4be21f. The object-presence probe now disables lazy fetching and has a local-only fallback origin. Independent Git tracing found zero fetch children across all four presence probes with HTTPS prohibited.

The full118-test suite, typecheck and repository check passed. The prior test-isolation finding is resolved; no remaining code defect found in the treeless cache, literal sparse checkout or write/publish behavior.