Module git_tree 

Git-tree-backed MemWriter — the second storage adapter. Buffers mutations in memory and applies them to a tree built via gix::object::tree::Editor, then advances the target ref via gix::Repository::commit_as.

No working tree is written: the mem’s content lives only in the multi-root mem-repo-git object store, one branch per mem. Each commit rebuilds the tree from the buffered op log against the snapshotted parent tree.

Snapshot + CAS

On the first mutation of a “session” (the period between two successful commits, or between construction and the first commit), the writer snapshots the current ref tip’s gix::ObjectId. That snapshot is the parents argument to gix::Repository::commit_as; gix’s underlying ref-edit transaction enforces PreviousValue::ExistingMustMatch(previous) for non-HEAD refs, which is the exact CAS guard we want. If a concurrent writer advanced the ref between snapshot and commit, the gix call returns gix::commit::Error::ReferenceEdit; we re-resolve the live tip and surface super::MemWriterError::HashMismatch with the new tip’s hex OID. That maps into [crate::EngineError::HashMismatch] so MCP agents see a stable _hash to retry with.

No internal retry loop: every CAS conflict bubbles up. Cross-process contention in Phase 1 is intentionally simple — concurrency hardening comes later (D7 in the design doc).

Structs

BranchBlob

One blob entry returned by read_branch_blobs — the mem-relative forward-slash path and the blob bytes. The list is sorted by path so callers (e.g. archive emitters) get deterministic ordering without a re-sort.

GitTreeMemWriter

Git-tree-backed implementation of MemWriter. Holds the gitdir path and target ref name; opens the gix::Repository per call (matches the [crate::vcs::GixVcs] pattern, since gix::Repository is Send but not Sync — its object-database cache uses interior mutability via RefCell).

Enums

BranchReadError

Errors surfaced by read_branch_blobs. Wraps the gix repo / reference / object operations so callers can map a missing branch or a malformed object to a structured error without re-importing gix’s error types.

Functions

read_branch_blobs

Walk every blob in the tree pointed at by <gitdir>:<ref_name>’s commit and return their (path, bytes) pairs sorted by path. The branch tip’s commit is peeled to a tree, then the tree is recursed breadth-first. Subtrees are descended; symlinks and non-blob entries are skipped (mem content is regular files only).