QA output created by 218
zero-length file:
Before: 0
After: 0
Sparse file (no blocks):
Before: 0
After: 0
Contiguous file:
Before: 1
After: 1
Write backwards sync, but contiguous - should defrag to 1 extent
Before: 10
After: 1
Write backwards sync leaving holes - defrag should do nothing
Before: 16
After: 16
Write forwards sync leaving holes - defrag should do nothing
Before: 16
After: 16