Adds assert_safe_same_host_deploy(local_src, remote_dst) to lib/common.sh:
pure, no SSH inside it, callable directly from a test with fixed inputs.
Returns 0 only when the two already-resolved paths are equal; refuses
(non-zero, message naming both paths + the 2026-07-31 incident) on any
other same-host mismatch.
This closes a real gap in the 2026-07-31 incident's original fix: the old
guard's two `case` blocks refused only containment (source-in-destination
or destination-in-source). A SIBLING directory — for example this very
worktree, archy-phase13, deploying onto TARGET_DIR's resolved symlink
target (archy, the main checkout) — is neither contained by nor containing
of the destination, so the old guard let it through and `rsync --delete`
would have mirrored the sibling onto the main checkout, deleting everything
the sibling lacks. Found while retargeting deploy-to-target.sh for D-19,
not a D-19 effect itself.
deploy-to-target.sh's guard block now calls assert_safe_same_host_deploy
instead of the two inline containment-only case blocks (old logic removed,
not left dead alongside the new call).
tests/production-quality/deploy-guard-same-host.sh pins all five
<behavior> cases (identical/contained/containing/sibling/unrelated)
against the function with no SSH, no rsync, no real deploy — including the
exact archy-phase13-vs-archy pair as the sibling-directory regression pin.
Manually confirmed non-vacuous: flipping the sibling fixture's expectation
to "allow" makes the test fail.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
