feature request: add ability to transform filesystems

Forwarding https://bugzilla.gnome.org/show_bug.cgi?id=671784

It would be great to have the ability to transform filesystems between different types.

There are a couple of options for very specific conversions:

tune2fs can convert from ext2/ext3 to ext4.

btrfs-convert can convert from ext2/3/4 or reiserfs to btrfs.

There are two options for generic transformation:

convertfs converts from virtually any filesystem type to virtually any one as long as they are both block-oriented and supported by Linux for read/write, and as long as primary filesystem supports sparse files. It is unfortunately no longer developed and only available in a few distros.

fstransform is a newer reimplementation of the same mechanism and is available in many distros.