TODO

* fstransform, fsmove: add persistence, i.e. the ability to resume a transformation
       after CTRL-C, power failure or similar interruptions

* fsmove: use a larger buffer (1MB) to speed up backward copy.
          beware of low free space!
          
* fsremap: add a graphical interface ? probably not so worth it...


WONTDO
* fsmove: if file system free space is critically low, launch 'xfs_fsr'
          to try and free some space before giving up.
  why not:
  LIMITED USEFULNESS: only for 'xfs' file system
  DANGEROUS: at least on linux with an almost-full source device
      xfs_fsr can WORSEN the problem by triggering 'loop write error' kernel errors,
      which mean the source device has not enough space to accommodate the loop file contents.
      typically this CORRUPTS the file system inside target (loop) device!


DONE in 0.9.3
* all: check FHS (Filesystem Hierarchy Standard) and decide where to
       put persistence data. decision: /var/tmp/fstransform/

* fsremap: add persistence, i.e. the ability to resume a transformation
       after CTRL-C, power failure or similar interruptions
       
* fstransform: also allow device to be UNMOUNTED instead of MOUNTED.
       gives easier integration with gparted, and guarantees
       that nobody is accessing the file-system inside device

DONE in 0.9.2          
* fsremap: preemptively check that last device block is writable.
       avoids troubles on linux with file-systems significantly smaller than device
