src/zlevis-fetch: added summary and improved zlevis-decrypt check

src/zlevis-fetch

@@ -3,8 +3,20 @@
 # Exit immediately if a command exits with a non-zero status
 set -e
 
+# Summary of the script's functionality
+summary="Decrypts a ZFS root pool with a TPM2.0 chip."
+
+# Display summary if requested
+if [ "$1" = "--summary" ]; then
+	echo "$summary"
+	exit 0
+fi
+
 # Check if zlevis-decrypt is present
-command -v zlevis-decrypt > /dev/null || exit 1
+if ! command -v zlevis-decrypt > /dev/null; then
+	echo "Script zlevis-decrypt is not present"
+	exit 1
+fi
 
 # Read ZFS dataset information.
 zfs list -Ho name,encryption,keystatus,encryptionroot,tpm:jwe | while IFS=$'\t' read -r ds enc keystatus encroot jwe; do
@@ -18,8 +30,8 @@ zfs list -Ho name,encryption,keystatus,encryptionroot,tpm:jwe | while IFS=$'\t'
                 echo "Unlocked $ds"
             else
                 echo "Failed to unlock $ds" >&2
-				exit 1
+		        exit 1
             fi
         fi
     fi
-done
+done