Add branching by rsync exit code

- Exit codes that should cause an exit, do so.
- Exit codes that indicate a temporary error, will now cause the script
  to wait and then try again.
Signed-off-by: Robert Spencer <rspencer@lbsd.net>

scripts/backstep-traceback-auto

@@ -24,6 +24,7 @@ import configparser
 import os
 import subprocess
 import sys
+import time
 
 parser = argparse.ArgumentParser(
     description="Automatic backup script using backstep-traceback."
@@ -109,7 +110,9 @@ else:
         if bwlimit > 0:
             syncopts.append("--bwlimit=" + str(bwlimit))
 
-for lv in ast.literal_eval(config.get(PERIOD, "backup_lvs")):
+stack = []
+
+for lv in reversed(ast.literal_eval(config.get(PERIOD, "backup_lvs"))):
     if args.only and args.only != lv:
         continue
 
@@ -163,7 +166,44 @@ for lv in ast.literal_eval(config.get(PERIOD, "backup_lvs")):
         )
     )
 
-    if not args.test:
-        EXIT_CODE = subprocess.call(command_line)
-    else:
-        print(command_line)
+    stack.append(command_line)
+
+#   Rsync Exit Values
+#   0      Success
+#   1      Syntax or usage error
+#   2      Protocol incompatibility
+#   3      Errors selecting input/output files, dirs
+#   4      Requested action not supported
+#   5      Error starting client-server protocol
+#   6      Daemon unable to append to log-file
+#   10     Error in socket I/O
+#   11     Error in file I/O
+#   12     Error in rsync protocol data stream
+#   13     Errors with program diagnostics
+#   14     Error in IPC code
+#   20     Received SIGUSR1 or SIGINT
+#   21     Some error returned by waitpid()
+#   22     Error allocating core memory buffers
+#   23     Partial transfer due to error
+#   24     Partial transfer due to vanished source files
+#   25     The --max-delete limit stopped deletions
+#   30     Timeout in data send/receive
+#   35     Timeout waiting for daemon connection
+
+exit_list = [0, 1, 2, 3, 4, 6, 13, 14, 20, 21, 22, 24, 25]
+wait_list = [5, 10, 11, 12, 23, 30, 35, 255]
+
+while stack:
+    task = stack.pop()
+
+    EXIT_CODE = subprocess.call(task)
+
+    if EXIT_CODE in exit_list:
+        sys.exit(EXIT_CODE)
+    elif EXIT_CODE in wait_list:
+        stack.append(task)
+
+        if args.verbose:
+            print("Sleeping...")
+
+        time.sleep(3030)