#!/bin/sh
# This is just for the record.
# This test is not run.

exit 0

cat <<\EOF

Prior to 5.0.91, ...

The problem:
  On a VFAT file system with coreutils-5.0.90, `mv FOO foo' removes the
  sole copy of the file named by both the source and destination arguments.

Demonstrate the problem, as root:

cd /tmp                                    \
  && dd if=/dev/zero of=1 bs=8192 count=50 \
  && mkdir mnt && mkfs -t vfat 1           \
  && mount -oloop 1 mnt && cd mnt          \
  && printf something important > foo      \
  && mv foo FOO
test -f FOO && echo PASS-1 || echo FAIL-1
ln foo bar
mv foo FOO
test -f FOO && echo PASS-2 || echo FAIL-2

And in case you actually do the above, you can do this to clean up:

  cd /tmp && umount /tmp/mnt && rm -r 1 mnt

Hey!  Can't create hard links on vfat.
The above `ln' evokes an `operation not permitted' failure.

This demonstrates the same thing with file system type `umsdos'
No hard links:

cd /tmp                                    \
  && dd if=/dev/zero of=1 bs=8192 count=50 \
  && mkdir mnt && mkfs -t msdos 1          \
  && mount -t umsdos -oloop 1 mnt && cd mnt \
  && printf something important > foo      \
  && mv foo FOO
test -f FOO && echo PASS-1 || echo FAIL-1
ln foo bar
mv foo FOO
test -f FOO && echo PASS-2 || echo FAIL-2

EOF