sparsify - make files sparse in-place

Make files with lots of 0's in them (much) smaller by making them sparse. Works
on any file system that supports FALLOC_FL_PUNCH_HOLE (two examples are btrfs
and ext4, haven't tried any others). This program might be buggy, so check
md5sums before and after. Makes files smaller than `cp --sparse=always' and
just as small as `dd conv=sparse'.

To install, just do something like `gcc sparse.c -o ~/bin/sparsify.unsafe'.

You can find licensing information in the LICENSE file.