Topic: include 'fstransform'?
I am the author of 'fstransform' (http://sf.net/projects/fstransform/) a program to non-destructively change the contents of a partition from one file-system type to another, in-place and without the need for any backup.
The program is still in beta stage and surely needs more thorough testing, but it's already usable - on Linux I have tested it on ext2, ext3, ext4, jfs, reiserfs and xfs.
Except for 'convertfs', which looks abandoned since 2005, I am not aware of any other tool with similar features.
In _extreme_ summary, fstransform uses this technique to change the file-system inside a partition while preserving all contaned files, directories, etc.: creates a sparse file as large as the device, formats it (mkfs) with the target file-system type, mounts it as a loop device (losetup), moves one by one all the files inside it, finally remaps the file onto the partition.
On the plus side, it needs no knowledge of file-systems implementation details: it only needs the initial file-system to support sparse files and ioctl(FS_IOC_FIEMAP) or the older ioctl(FIBMAP).
On the down side, it is relatively slow: on a fast magnetic disk, transforming a 250GB file-system may take up to 10 hours.
I am proposing to add support to gparted to detect and launch fstransform as an external tool, and I can implement personally the required patches,
but I am new to gparted and I must admit I don't know if such tool can be considered in scope for gparted - personally, I would consider it a nice addition, but I am obviously biased...