fix: harden rsyncshot destination, rotation, and mount handling

Refuse to run when REMOTE_PATH or MOUNTDIR is empty or non-absolute. A blank config value otherwise resolves the destination to the filesystem root, where rotation runs rm -rf and --delete.

Run the rotation cp/mv/rm as bare command names in remote mode, resolved by the remote PATH, instead of hardcoded /usr/bin paths that broke on remotes whose binaries live elsewhere. Resolve the real binary via command -v in local mode.

Pass rsync -R so each source is stored under its full path. Two includes sharing a basename (/usr/local/bin and /usr/bin) previously both mapped to latest/bin, and the second sync's --delete wiped the first. This changes the stored layout: /usr/local/bin now lives at latest/usr/local/bin instead of latest/bin. /home and /etc are unchanged.

Add rsync --numeric-ids so /etc and /home ownership survives a restore when the destination has a different passwd/group database.

Match mount points exactly via is_mounted() instead of a substring grep of /proc/mounts, so /media/backup no longer matches /media/backup2, paths compare literally, and mount points with spaces work.

Reject a retention count below 1, which previously still created one snapshot. Drop the grep "|| echo 0" that emitted a stray second line, assemble ssh options as arrays, and quote the RSYNC_RSH identity path.

Extract derive_paths() and is_mounted() as sourceable functions and add unit, rsync-flag, and gated remote-mode test suites. The suite now runs 36 tests, and shellcheck is clean across the script and tests.

1 files changed, 60 insertions, 0 deletions

diff --git a/tests/cases/test_remote.sh b/tests/cases/test_remote.sh
new file mode 100644
index 0000000..c2ee75e
--- /dev/null
+++ b/tests/cases/test_remote.sh
@@ -0,0 +1,60 @@
+#!/usr/bin/env bash
+# ==============================================================================
+# Remote (SSH) Mode Tests
+# ==============================================================================
+# First coverage of the remote path — backup + rotation run over SSH. The whole
+# transfer and rotation happen via ssh to localhost, which exercises run_cmd's
+# remote branch and the bare cp/mv/rm rotation commands. Gated: if root can't
+# ssh to localhost with key auth, the suite skips rather than fails, so machines
+# without loopback SSH still pass.
+
+source "$(dirname "${BASH_SOURCE[0]}")/../lib/test_helpers.sh"
+
+remote_available() {
+    ssh -o BatchMode=yes -o ConnectTimeout=5 localhost true 2>/dev/null
+}
+
+# ------------------------------------------------------------------------------
+# Backup + rotation over SSH-to-localhost
+# ------------------------------------------------------------------------------
+test_remote_backup_and_rotation() {
+    setup_test_env
+    cat > "$TEST_CONFIG_DIR/config" <<EOF
+REMOTE_HOST="localhost"
+REMOTE_PATH="$TEST_BACKUP_DIR"
+EOF
+    create_test_includes >/dev/null
+    create_test_excludes >/dev/null
+
+    # Two runs to exercise rotation over SSH (MANUAL.0 rotates to MANUAL.1)
+    INSTALLHOME="$TEST_CONFIG_DIR" "$SCRIPT_PATH" manual 2 >/dev/null 2>&1
+    INSTALLHOME="$TEST_CONFIG_DIR" "$SCRIPT_PATH" manual 2 >/dev/null 2>&1
+
+    assert_dir_exists "$TEST_BACKUP_DIR/$HOSTNAME/MANUAL.0" "remote backup should create MANUAL.0" || { teardown_test_env; return 1; }
+    assert_dir_exists "$TEST_BACKUP_DIR/$HOSTNAME/MANUAL.1" "remote rotation should produce MANUAL.1" || { teardown_test_env; return 1; }
+    assert_file_exists "$TEST_BACKUP_DIR/$HOSTNAME/latest$TEST_SOURCE_DIR/home/testuser/file1.txt" "remote backup should copy files" || { teardown_test_env; return 1; }
+
+    teardown_test_env
+}
+
+# ------------------------------------------------------------------------------
+# Run tests
+# ------------------------------------------------------------------------------
+run_remote_tests() {
+    echo ""
+    echo "Running remote (SSH) tests..."
+    echo "------------------------------------------------------------"
+
+    if ! remote_available; then
+        echo "  SKIP: root cannot ssh to localhost with key auth — skipping remote tests"
+        return 0
+    fi
+
+    run_test "remote backup + rotation over SSH" test_remote_backup_and_rotation
+}
+
+# Run if executed directly
+if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then
+    run_remote_tests
+    print_summary
+fi