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, 4 insertions, 4 deletions

diff --git a/tests/cases/test_cron.sh b/tests/cases/test_cron.sh
index 2fdb6f5..5c9bbfa 100755
--- a/tests/cases/test_cron.sh
+++ b/tests/cases/test_cron.sh
@@ -39,7 +39,7 @@ EOF
     create_test_excludes
 
     # Run setup (will fail on some checks but should still add cron)
-    sudo INSTALLHOME="$TEST_CONFIG_DIR" SCRIPTLOC="/tmp/rsyncshot-test" RSYNCSHOT_SKIP_MOUNT_CHECK=1 "$SCRIPT_PATH" setup 2>&1 >/dev/null || true
+    sudo INSTALLHOME="$TEST_CONFIG_DIR" SCRIPTLOC="/tmp/rsyncshot-test" RSYNCSHOT_SKIP_MOUNT_CHECK=1 "$SCRIPT_PATH" setup >/dev/null 2>&1 || true
 
     # Check crontab contains rsyncshot entries
     local crontab_content
@@ -72,8 +72,8 @@ EOF
     create_test_excludes
 
     # Run setup twice
-    sudo INSTALLHOME="$TEST_CONFIG_DIR" SCRIPTLOC="/tmp/rsyncshot-test" RSYNCSHOT_SKIP_MOUNT_CHECK=1 "$SCRIPT_PATH" setup 2>&1 >/dev/null || true
-    sudo INSTALLHOME="$TEST_CONFIG_DIR" SCRIPTLOC="/tmp/rsyncshot-test" RSYNCSHOT_SKIP_MOUNT_CHECK=1 "$SCRIPT_PATH" setup 2>&1 >/dev/null || true
+    sudo INSTALLHOME="$TEST_CONFIG_DIR" SCRIPTLOC="/tmp/rsyncshot-test" RSYNCSHOT_SKIP_MOUNT_CHECK=1 "$SCRIPT_PATH" setup >/dev/null 2>&1 || true
+    sudo INSTALLHOME="$TEST_CONFIG_DIR" SCRIPTLOC="/tmp/rsyncshot-test" RSYNCSHOT_SKIP_MOUNT_CHECK=1 "$SCRIPT_PATH" setup >/dev/null 2>&1 || true
 
     # Count rsyncshot entries
     local crontab_content hourly_count
@@ -105,7 +105,7 @@ EOF
     create_test_excludes
 
     # Run setup
-    sudo INSTALLHOME="$TEST_CONFIG_DIR" SCRIPTLOC="/tmp/rsyncshot-test" RSYNCSHOT_SKIP_MOUNT_CHECK=1 "$SCRIPT_PATH" setup 2>&1 >/dev/null || true
+    sudo INSTALLHOME="$TEST_CONFIG_DIR" SCRIPTLOC="/tmp/rsyncshot-test" RSYNCSHOT_SKIP_MOUNT_CHECK=1 "$SCRIPT_PATH" setup >/dev/null 2>&1 || true
 
     # Check custom job still exists
     local crontab_content