Neil
34ae0933e4
* fix(worktrees): remove repeated scans and keep prepared checkouts fresh * fix(worktrees): reclaim unlocked fallback preparations safely * refactor(worktrees): simplify creation ownership and idle maintenance * fix(git): keep ref maintenance armed after an index-only pass An idle attempt that found the pack index due but refs still cooling down returned without rescheduling, so loose refs from the arming fetch waited for the next write instead of the ref cooldown.
7.5 KiB
Git Compatibility Policy
Scope
Orca executes the user's Git binary on three kinds of execution host: native, WSL, and SSH. Each host can have a different Git version, so compatibility state must be scoped to the host that actually runs the command.
Git 2.25 is the core-workflow compatibility baseline for command selection. It
is the oldest line that covers Orca's baseline use of porcelain v2, branch --show-current, restore, and sparse checkout. Optional features that need a
newer Git must degrade safely and cache the missing capability. Orca does not
currently block older Git at startup, but new command construction should not
assume features introduced after this baseline.
Capability Rules
When a newer Git feature materially improves correctness or performance:
- Keep a baseline-compatible command or parser as the fallback.
- Detect rejection with a narrow predicate for that option or subcommand.
- Run the preferred command through
GitCapabilityCacheso a rejection is remembered for the native host, WSL distro, or SSH provider that produced it. - Retry after the cache interval so an in-place Git upgrade self-heals without restarting Orca.
- Test the first fallback, later calls that skip the rejected probe, concurrent probe coalescing, and execution-host isolation where applicable.
Do not branch only on a parsed git --version. Vendor builds can backport
features, and wrappers can report a host version that differs from the binary
used inside WSL or SSH. A behavior probe plus a precise fallback is the final
authority.
Current Capabilities
| Capability | Preferred behavior | Compatibility behavior |
|---|---|---|
fetch-no-write-fetch-head |
Fetch a private rebase ref without changing worktree-local FETCH_HEAD |
Serialize all Orca fetch/pull operations per worktree Git directory before Git 2.29 |
worktree-list-z |
NUL-delimited worktree paths with prunable marks |
Line-block parser for Git before worktree list -z (2.36); the prunable/locked annotations still parse on Git 2.31–2.35, and a path-existence probe restores prunable detection for Git before 2.31 |
worktree-add-lock-reason |
Create a prepared checkout with its ownership marker already present | Before Git 2.33, add without checkout, then exclusively create the same reason marker before materializing files |
rev-parse-path-format |
Absolute repo metadata paths | Resolve legacy relative output against the scanned repo |
for-each-ref-exclude |
Exclude remote HEAD before the output limit | Request extra refs, then filter remote HEAD in Orca |
merge-tree-write-tree |
Derive real-merge conflicts and no-op tree proofs | Omit the conflict summary and keep conservative branch cleanup behavior before Git 2.38 |
merge-tree-merge-base |
Supply the already-resolved merge base | Use the older two-commit merge-tree --write-tree form |
Prepared creation registers and locks without checking out files while its shared
exact-base fetch runs. A cancellable in-process barrier waits for fetch settlement,
including offline failure, then resolves the current commit OID on the owning host
and materializes files once. Existing preparations queue a tip refresh on that same
barrier before a create can claim them. Finalization still resolves the latest base
and runs the post-checkout hook only when attaching the requested branch. This uses
baseline-compatible rev-parse and reset --hard; the barrier never enters Git
transport options or the remote wire.
Placeholders That Fail Open
GitCapabilityCache records commands Git rejects. A git log --format
placeholder Git does not know is not rejected: Git echoes it verbatim and exits
zero, so there is no error to remember and no probe to cache. Ask for both forms
in one record and pick at parse time.
| Placeholder | Preferred behavior | Compatibility behavior |
|---|---|---|
%(decorate:…) |
Git 2.43 separates commit decorations with \x1f, so ref names containing commas survive |
The same record also carries %D (Git 2.10); an unexpanded %(decorate placeholder selects it, at the cost of comma-splitting |
Why Not simple-git
simple-git is a process wrapper around the installed Git binary. Its custom
options and raw API pass arguments through to Git, so it cannot make a newer
flag work on an older binary or choose Orca's semantic fallback automatically.
It provides version reporting and subprocess queueing, but Orca already needs
its own WSL/SSH routing, cancellation, tracing, redaction, process cleanup, and
bounded output handling. Replacing the runner would move—not remove—the
capability problem.
CI Contract
PR checks run the capability contract against real Git 2.25.5, 2.38.1, and
2.49.1 binaries. This spans the pre-2.29 serialized FETCH_HEAD fallback, the transitional
merge-tree --write-tree behavior before --merge-base, and current Git.
The three lanes run in parallel and each Git call in the container lanes costs a container start, so their wall clock is runner contention, not Git. Build the 2.25.5 binary and pull the images before the lanes start: anything heavy left running alongside them is charged to whichever boundary case is in flight and surfaces as a Vitest timeout rather than as a slow setup step.
The idle maintenance contract also verifies multi-pack-index write and packed
object reads. The command arrived in Git 2.20 and needs no newer-Git fallback;
Orca uses only index metadata writes, respecting core.multiPackIndex=false.
Keep the unit tests alongside that matrix. They cover concurrent probes, native/WSL/SSH/relay isolation, and error-stream shapes that a single real binary invocation cannot exercise deterministically.