* perf(git): overlap getBranchCompare's head-of-chain reads
Four git spawns ran strictly in series before any compare work began:
branch --show-current, the base-ref probe, rev-parse HEAD, and rev-parse <base>.
Three are independent -- compareRef is display-only metadata and HEAD's oid does
not depend on the base ref -- so they now run concurrently. The fourth was
redundant outright: the probe already runs `rev-parse --verify --quiet
<ref>^{commit}` and discarded the oid it printed, which was then re-resolved by a
second spawn. resolveWorktreeBaseCommitOid returns that oid so it can be reused;
hasWorktreeBaseCommitRef now delegates to it, leaving its other 4 callers
untouched.
3.6-3.7x on a short remote base label (192ms -> 52ms), 1.44x on an
already-qualified refs/... base, which skips the probe by design.
Reuse is keyed by ref: resolveWorktreeAddBaseRef returns at its first successful
candidate, so only that ref's oid is ever read back. Peeling is safe because only
refs/heads and refs/remotes candidates reach the probe, where ^{commit} is a
no-op.
No new git features: this removes a spawn rather than adopting an option.
Co-authored-by: Orca <help@stably.ai>
* fix(git): preserve compare semantics across providers
Co-authored-by: Orca <help@stably.ai>
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Co-authored-by: Orca <help@stably.ai>
