File explaining the error codes that assign, assign_wrapper, and

tbswap can return - they use their return value to communicate some
information. Text is from Chad.

doc/errorcodes.txt

+This file contains notes about the error codes from a few testbed programs
+that provide information more than sucess/failure in their return values.
+
+NOTE: It's possible that this file has gotten out of sync with reality, so sure
+to check the program in question before using these.
+
+assign:
+   0 - success
+   1 - failure; try assign again
+   2 - failure; do not try assign again - the given top can never map to
+       the given ptop
+
+assign_wrapper:
+   0 - success
+   >0 = failure, returncode is 1 OR a subset of:
+    2 - max_concurrent violation
+    4 - bandwidth violation
+    8 - linkusers violation
+   16 - desires violation
+   32 - unassigned (e.g., not enough nodes, I think)
+   64 - "recoverability":
+        Think of this as "clean";
+        indicates that assign_wrapper did not get past the assigning phase;
+        [If a swap-modify fails, this must be set for recovery to happen]
+
+tbswap:
+   0 - success
+   1 - failure not involving assign_wrapper
+   >1 - failure from assign_wrapper;
+        returncode is whatever assign_wrapper returned,
+        WITHOUT the '64' bit set.