# WASI patches for Git foundation (SAU-21)

All crates here are complete crates.io source archives, with their original licenses.
`Cargo.toml` uses local `[patch.crates-io]` paths. No upstream submission has been made.
Changes apply only to `target_os = "wasi"`; native paths retain upstream behavior.
No parallel, signal/interrupt, or worktree-mutation features are enabled.
SAU-24 enables blocking-network-client and a custom wasi:http backend (no curl/reqwest).

## gix-tempfile 26.0.0: no OS PID on WASI

Exact panic: `src/forksafe.rs`, `ForksafeTempfile::new`, field
`owning_process_id: std::process::id()`. Ref transactions acquire gix-lock files,
which register these tempfiles. This is registry fork ownership, **not filename generation**.
`std::process::id()` panics with `no pids on this platform` on wasm32-wasip2.

Patch: a private `process_id()` returns 0 on WASI (no fork, registry is per component
instance), and the native OS PID elsewhere. Use it in creation and both registry
cleanup methods. Random tempfile naming and exclusive file creation are unchanged.
Verified the unpatched ref-updating commit panics; patched commits and index writes pass.

## gix-pack 0.77.0: owned pack/index/multi-index bytes

`src/lib.rs`: WASI's `MMap` is `Vec<u8>` and the shared `mmap::read_only()` helper
uses `std::fs::read`. Other targets retain memmap2. This covers the pack data,
pack index, and multi-pack-index constructors that all use this helper.
memmap2 0.9.11 selects its unsupported stub on WASI; the original map call returns
`ErrorKind::Unsupported` rather than reading a pack.

Tests generate a tiny pack via `gix-pack`'s `data::output::bytes::FromEntriesIter`;
the simple v2 index is encoded in the test (fanout, sorted IDs, CRCs, offsets,
pack checksum, index checksum). This avoids enabling the broken streaming-input
feature just for the test. A second test packs all commit/tree/blob objects,
removes every loose object copy and stores the branch only in `packed-refs`,
reopens the repository and reads history, paths, branches,
blob contents, and creates/reads its index. No shell or Git executable is used.

## gix-odb 0.87.0: owned loose-object bytes

Additional breakage found by the full tests: `src/store_impls/loose/find.rs`
uses memmap2 for *every loose object read and header lookup*, not just packs.
Without this patch logs and tree/index construction return `unsupported`.
Use the same platform-dependent `gix_pack::MMap` backing and std file reads on WASI.
Decompression, missing-object handling, and validation remain upstream code.

## gix-index 0.58.0: read index without mmap

`src/file/init.rs`: WASI reads into a Vec from the already opened file and rewinds
that same handle before checksum streaming. This preserves a single inode snapshot
across concurrent atomic index replacements. Native mmap code is unchanged.
Nonempty v2 index round trip and checksum-corruption rejection pass under WASI.

## filetime 0.2.29: metadata timestamp readers

Additional runtime panic found after the mmap fixes: filetime routes WASI to its
generic wasm backend, whose metadata timestamp readers call `unimplemented!()`.
`src/lib.rs` now selects `src/wasi.rs` before that backend. It obtains modified,
accessed, and optional creation times through std Metadata; inaccessible modified/
accessed times fall back to zero, because the upstream API cannot return an error.
Symlink time mutation remains an explicit Unsupported error; ordinary file-time
setters retain the upstream std File::set_times implementation. Metadata reads are
exercised by index tests; timestamp setters and symlink mutation are not exercised.

## gix-ref 0.69.0: disable packed-refs mmap through existing API

No additional vendored crate is needed. On WASI, `src/repo.rs::open` calls
`repo.refs.set_packed_buffer_mmap_threshold(u64::MAX)` before any reference lookup.
Upstream `store/packed/buffer.rs::Buffer::open` uses owned bytes for files at or
below that threshold; otherwise it uses unsupported memmap2. The default threshold
is 32 KiB. Native repository handles retain the upstream default.

Regression `large_packed_refs_head_branches_and_log` writes 65,638 bytes of sorted
packed refs (1,025 branches), removes the loose HEAD branch and reopens through
our helper. It checks symbolic HEAD, all branch tips/current flag, HEAD log order,
and log by a non-HEAD packed branch. Before the fix this fails on WASI with
`HEAD: Could not open packed refs`; with the fix it passes. Packed refs also consume
owned linear memory; this is not a repository size limit.

## Intentionally disabled / work for later cards

- `worktree-mutation`: `gix-worktree-state` depends on `io-close 0.3.7`; it lacks
  a WASI File close implementation (`no method close for File`). Add a WASI backend
  or write the checkout engine using std file writes. Do not silently ignore writes.
- `blocking-network-client` is now enabled by SAU-24: see the streaming-input patch below.
- `gix-commitgraph` remains unpatched: `src/file/init.rs` maps commit-graph files
  with memmap2, unsupported on WASI. Current `log` explicitly uses
  `use_commit_graph(false)` and does not need this cache. This is NOT disabled
  centrally by `repo::open`. Later merge-base/ahead-behind/revision operations must
  disable or avoid commit-graph loading (including direct graph APIs), or patch
  that crate to read owned bytes before using it. Some high-level gix walks fall
  back to the object database on graph-load errors; direct graph loading can fail.
  Existing native Git `objects/info/commit-graph` files are not fixture-tested here.
- No signals or threads are provided; keep `interrupt` and `parallel` off.
- No large-repo memory benchmark was run. Pack + pack-index bytes are held in
  32-bit linear memory, in addition to decoded objects; whole-pack reads have a
  materially higher resident-memory cost than demand-paged native mmap. The tiny
  fixture is 53 pack bytes for one blob. No peak RSS/linear-memory measurement.
- Multi-pack-index reading uses the patched helper but is not fixture-tested here.
  Delta packs, split index, and external Git-generated fixtures are not tested.

## SAU-24: gix-pack 0.77.0 streaming-input on WASI

Existing vendored crate extended (no additional crate patch). In `Cargo.toml` and
`Cargo.toml.orig`, allow gix-tempfile under
`cfg(any(not(target_arch = "wasm32"), target_os = "wasi"))`. Browser wasm is still
excluded; gix-tempfile remains `default-features = false`, so no signals are added.
The foundation's PID patch applies unchanged.

Additional compile error exposed by enabling the feature: bundle writer's
`new_pack_file_resolver` and `resolve_entry` explicitly used `memmap2::Mmap`.
Change those three type annotations in `src/bundle/write/mod.rs` to `crate::MMap`,
reusing the existing owned-byte WASI helper and keeping native mmap behavior.
No pack/index format change. No upstream submission made.

Verified by local fake Git HTTP servers through wasi:http in cargo.build: V1
clone writes a received 227-byte / 3-object pack and real index, updates tracking
refs and checks out exact bytes; V2 shallow clone writes the shallow boundary.
This tests the bundle writer, not merely hand-encoded pack indexes. Pack input
is streamed to a tempfile; indexing still reads a whole-pack Vec on WASI and
therefore needs 32-bit memory proportional to pack size. Use clone `depth` to
reduce history. No large-repo memory measurement.

## Sources inspected

- https://raw.githubusercontent.com/GitoxideLabs/gitoxide/gix-v0.90.0/gix-ref/src/store/file/mod.rs
- https://raw.githubusercontent.com/GitoxideLabs/gitoxide/gix-v0.90.0/gix-ref/src/store/packed/buffer.rs
- https://raw.githubusercontent.com/GitoxideLabs/gitoxide/gix-v0.90.0/gix/src/types.rs
- https://raw.githubusercontent.com/GitoxideLabs/gitoxide/gix-v0.90.0/gix-commitgraph/src/file/init.rs
- https://raw.githubusercontent.com/GitoxideLabs/gitoxide/gix-v0.90.0/gix/src/revision/walk.rs

- https://raw.githubusercontent.com/GitoxideLabs/gitoxide/gix-v0.90.0/gix/Cargo.toml
- https://static.crates.io/crates/gix-tempfile/gix-tempfile-26.0.0.crate
- https://static.crates.io/crates/gix-pack/gix-pack-0.77.0.crate
- https://static.crates.io/crates/gix-index/gix-index-0.58.0.crate
- https://static.crates.io/crates/gix-odb/gix-odb-0.87.0.crate
- https://raw.githubusercontent.com/RazrFalcon/memmap2-rs/v0.9.11/src/stub.rs
- https://raw.githubusercontent.com/alexcrichton/filetime/0.2.29/src/wasm.rs
- https://static.crates.io/crates/filetime/filetime-0.2.29.crate