WIP Fixed ENOSPC issues with zero-granularity blocks

tests/corrupt.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python
+
+import struct
+import sys
+import os
+
+def main(*paths):
+    # find most recent block
+    file = None
+    rev = None
+    for path in paths:
+        try:
+            nfile = open(path, 'r+b')
+            nrev, = struct.unpack('<I', nfile.read(4))
+
+            assert rev != nrev
+            if not file or ((rev - nrev) & 0x80000000):
+                file = nfile
+                rev = nrev
+        except IOError:
+            pass
+
+    # go to last commit
+    tag = 0
+    while True:
+        try:
+            ntag, = struct.unpack('<I', file.read(4))
+        except struct.error:
+            break
+
+        tag ^= ntag
+        file.seek(tag & 0xfff, os.SEEK_CUR)
+
+    # lob off last 3 bytes
+    file.seek(-((tag & 0xfff) + 3), os.SEEK_CUR)
+    file.truncate()
+
+if __name__ == "__main__":
+    main(*sys.argv[1:])