glm-5.3-flash
86bf5a0cf0
Structural decision (OQ-09 resolved): alkgit follows the alktty/ alktunnels template — a single published protocol crate on alkcall channels, no binary, no front doors. - ADR-010 supersedes ADR-001 (crate decomposition) and ADR-006 (http router factory); both marked Superseded - Single crate at repo root: Cargo.toml with gix feature (default-on backend implementations; wire layer compiles without it — gix-hash always-on with sha1 per the compile-time-rejected invariant), crates/ workspace deleted, src/lib.rs stub in place - doors.md replaces http.md/ssh.md/alkgitd.md: alkhttp git-feature sequencing (after first publish), alkssh requirement (fixed-grammar exec dispatch), native alk/git path, downstream assembly - backend.md replaces storage.md: GitRegistry/GitRefs/GitPackGen/ GitPackIngest traits (ingest validates, refs commits — single CAS home), gix feature encodes POC-2 prerequisites - transport.md reframed for the single crate; backend traits replace hook traits in the public API - OQ-09 resolved (all five sub-decisions in ADR-010), OQ-01 resolved (subsumed), OQ-03 narrowed to publish-freeze, OQ-08 narrowed to registry identity + vault placement, OQ-07 rescoped to the gix feature's registry impl - vision.md v2: single-binary/monorepo framing corrected as init-agent artifact; POC checklist marked complete - AGENTS.md + .opencode agent specs updated to the new shape Verification: cargo build (default + no-default-features), cargo test --all-features, clippy --all-features -D warnings, fmt --check all pass. Third review round: zero critical, all warnings/suggestions addressed (GitPackGen signature amended in ADR-004, stale anchors fixed, ADR-006 body tense normalized, CAS split stated, vision residuals cleaned).
129 lines
5.5 KiB
Markdown
129 lines
5.5 KiB
Markdown
---
|
|
status: draft
|
|
last_updated: 2026-09-21
|
|
---
|
|
|
|
# alkgit: Git Smart Protocol (wire layer)
|
|
|
|
## What it is
|
|
|
|
The wire half of the `alkgit` protocol crate: pkt-line session substrates,
|
|
protocol V2 state machines (advertisement, ls-refs, fetch, receive-pack),
|
|
and the substrate types that keep doors and handlers from touching
|
|
`futures_io` or raw packetline APIs. Depends on alkcall and — only under
|
|
the `gix` feature — the backend implementations (ADR-010). The wire layer
|
|
itself is backend-trait-only, which is what makes `default-features =
|
|
false` compile without gix.
|
|
|
|
## Substrate layer (ADR-005)
|
|
|
|
Two session entry points over one state-machine core. ADR-005 owns the
|
|
full decision (what each substrate owns and why); the surface is:
|
|
|
|
- **Duplex session** (the `alk/git` ALPN producer, channels-opened git
|
|
sessions, embedder stream doors) — input: (peer identity, resolved repo
|
|
id, duplex stream, `Limits`). Encapsulates the split/compat/packetline
|
|
bridge, the request reader (delim-aware parsing, `reset()` discipline,
|
|
break-on-error), and the sideband writer.
|
|
- **Stateless session** (smart-http doors, e.g. alkhttp's future `git`
|
|
feature) — input: (peer identity, resolved repo id, request-reader,
|
|
response-writer, `Limits`) per http POST; adds the http-framing rules
|
|
(capability-dump skip, flush-only responses, probe handling). IO-abstract:
|
|
the door supplies reader/writer; see [doors.md](doors.md) for the
|
|
mounting.
|
|
|
|
Both substrates feed the same V2 state machines; statelessness is a
|
|
substrate property (per-request state), not a protocol fork.
|
|
|
|
## Protocol core (ADR-003: V2-first)
|
|
|
|
### Advertisement
|
|
|
|
- Emitted once per duplex session (never between commands — real git
|
|
hangs on re-advertisement); per-request-set on http (stateless: the
|
|
client re-sends the dump).
|
|
- Honest capability list: exactly what we serve (`ls-refs=unborn`,
|
|
`fetch=wait-for-done` for the v1 done-path policy — ADR-003 pins the
|
|
values; OQ-02 may extend them when multi-round lands,
|
|
`object-format=sha1`). Unimplemented features are declined by omission
|
|
(validated against real git, POC-1). `git-upload-archive` is not
|
|
served (fixed refusal — ADR-008's never-execute rule, ssh analog in
|
|
doors.md).
|
|
|
|
### ls-refs
|
|
|
|
- Parse `command=ls-refs` (peel, symrefs, ref-prefix), stream ref lines
|
|
from the backend's listing, flush. `ref-prefix` filtering is
|
|
client-driven.
|
|
|
|
### fetch
|
|
|
|
- Parse wants/haves/done/args; object-format check (reject mismatches —
|
|
POC-1 to-do).
|
|
- Negotiation policy (v1 initial): full-closure pack on `done`
|
|
(POC-validated). Multi-round ack/NAK negotiation: **OQ-02**.
|
|
- Pack generation via `GitPackGen` (ADR-004), streamed over sideband on
|
|
duplex / sideband-in-response on http; generation runs on
|
|
`spawn_blocking` with the owned handle moved in (POC-2's shape: store
|
|
shared, handle per session, generation on blocking threads).
|
|
- Round/haves budgets enforced here (ADR-009).
|
|
|
|
### receive-pack (push)
|
|
|
|
- Parse update requests (`<old> <new> <ref>` + shallow lines), ingest the
|
|
pack stream (POC-3-verified: request bodies stream), apply CAS
|
|
transactions, emit status report. The capability set, shallow policy,
|
|
CAS timing, and exact status-report shape are OQ-04's investigation
|
|
target (design intent: shape per OQ-04's resolution).
|
|
- Ingestion via `GitPackIngest` (ADR-004); validation pending — **OQ-04**
|
|
(includes the receive-pack version surface, which ADR-003's fetch-V2
|
|
decision does not cover).
|
|
|
|
### Error taxonomy
|
|
|
|
- io errors are terminal (session ends); protocol errors map to pkt-line
|
|
error bands (duplex) or http status + body (stateless). Substrate-level
|
|
`thiserror` enum; no panics in library code (convention 2).
|
|
|
|
## Limits
|
|
|
|
Every session carries `Limits` (ADR-009): negotiation rounds, haves per
|
|
round, receive-pack max size, wall clock, sideband chunk size (fixed
|
|
65000), advertisement ref cap. Missing `Limits` is a type-level error.
|
|
|
|
## Public API surface (v1)
|
|
|
|
Crate-root re-exports (alktty pattern; the full list in
|
|
[backend.md](backend.md) §public API): `GitAdapter` + `register_openable`,
|
|
`GitSession`, substrate types, `Limits`, the backend traits (ADR-010's
|
|
seam), protocol error enums; gix-feature types under the feature.
|
|
Publish-freeze point: **OQ-03**.
|
|
|
|
## Design Decisions
|
|
|
|
| ADR | Decision | Summary |
|
|
|---|---|---|
|
|
| [002](decisions/002-front-door-blind-core.md) | Session boundary | duplex + stateless entry points |
|
|
| [003](decisions/003-protocol-v2-first.md) | V2-first | honest advertisement, V0/V1 declined |
|
|
| [004](decisions/004-pack-pipeline.md) | Pack pipeline | generation on blocking threads, O(counts) |
|
|
| [005](decisions/005-session-substrate-types.md) | Substrate types | request reader, sideband sink, http framing rules |
|
|
| [009](decisions/009-bounded-resources-budget.md) | Budgets | `Limits` in every session tuple |
|
|
| [010](decisions/010-pure-protocol-crate.md) | Pure protocol crate | wire layer is backend-trait-only |
|
|
|
|
## Open Questions
|
|
|
|
- **OQ-02**: V2 multi-round negotiation (open — efficiency, not
|
|
correctness).
|
|
- **OQ-04**: receive-pack state machine + validation (deferred(unclear)).
|
|
- **OQ-03**: publish/API freeze (partially resolved — single-crate shape
|
|
settled by ADR-010).
|
|
- **OQ-05**: sha256 policy (deferred(scope)).
|
|
|
|
## References
|
|
|
|
- `docs/research/poc-1-findings.md`, `docs/research/poc2-findings.md`,
|
|
`docs/research/poc3-findings.md` (the normative wire behavior —
|
|
observed against real git, not docs' grammar)
|
|
- `docs/research/git-protocol.md` (inventory + observed corrections)
|
|
- `docs/research/gitoxide.md` §"Wire format" (packetline contracts)
|
|
- alktty `wire.rs`/`session.rs`/`adapter.rs` (the template's half shapes) |