feat: install pre-pacman ZFS snapshot hook on ZFS-root systems

archsetup took sanoid from install-archzfs but never ported the pre-pacman snapshot hook, so a ZFS-root install had no transaction-triggered rollback point — the working setup only existed as a hand-placed script on velox, lost on reinstall. Add configure_pre_pacman_snapshots(): a PreTransaction pacman hook plus a self-pruning script that keeps the 10 most recent pre-pacman snapshots (sanoid ignores them — they aren't autosnap_ names). It's gated to ZFS-root and runs late in boot_ux, so the hook doesn't fire during the install's own package operations and the first snapshot is the fresh system.

The script ships as scripts/zfs-pre-snapshot, made ZFS_PRE_* env-overridable so the pruning logic is unit-testable. Unit tests drive it against a fake zfs (creates a snapshot, prunes the oldest past KEEP, ignores non-pre-pacman snapshots, honors the lockfile interval, warns on failure); a Testinfra test asserts the hook and script land on a ZFS install; the orchestrator test pins the new boot_ux substep.

1 files changed, 16 insertions, 0 deletions

diff --git a/scripts/testing/tests/test_boot.py b/scripts/testing/tests/test_boot.py
index 78b4404..e442682 100644
--- a/scripts/testing/tests/test_boot.py
+++ b/scripts/testing/tests/test_boot.py
@@ -65,3 +65,19 @@ def test_zfs_has_sanoid(host):
     if not host.exists("zfs"):
         pytest.skip("ZFS not installed (non-ZFS system)")
     assert host.exists("sanoid"), "ZFS system should have sanoid installed"
+
+
+def test_zfs_pre_pacman_snapshot_hook(host):
+    # archsetup installs a PreTransaction pacman hook + a self-pruning script so
+    # every pacman transaction is preceded by a rollback snapshot (configure_
+    # pre_pacman_snapshots, run late in boot_ux). ZFS-root only.
+    if not host.exists("zfs"):
+        pytest.skip("ZFS not installed (non-ZFS system)")
+    script = host.file("/usr/local/bin/zfs-pre-snapshot")
+    assert script.exists and script.is_file, "pre-pacman snapshot script missing"
+    assert script.mode & 0o111, "pre-pacman snapshot script is not executable"
+    hook = host.file("/etc/pacman.d/hooks/zfs-snapshot.hook")
+    assert hook.exists and hook.is_file, "zfs-snapshot.hook missing"
+    assert "PreTransaction" in hook.content_string, "hook not PreTransaction"
+    assert "/usr/local/bin/zfs-pre-snapshot" in hook.content_string, \
+        "hook does not exec the snapshot script"