Three problems with install.sh --commit:
1. No validation: non-hex or too-short arguments passed through to git,
producing misleading errors.
2. Fetch failure swallowed by || true: abbreviated SHAs are refused by
GitHub's server ("couldn't find remote ref"), but the error was
silently ignored.
3. Checkout failure not checked: git checkout --detach with a missing
object produces a misleading "does not take a path argument" error
and the install continues unpinned, exiting 0.
Fix:
- Validate --commit is a 7-40 hex string up front
- Remove || true from fetch; fail with actionable message directing
users to full 40-char SHAs
- Check git checkout --detach result and fail hard on error
Fixes#87268
eac1f65340