git-mv is broken in master

Hi,

With the current master I get the following:

    $ git-mv README README-renamed
    fatal: can not move directory into itself, source=README, destination=README-renamed

Which is buggy. The culprit seems to be the test

    if (!bad &&
        !strncmp(destination[i], source[i], strlen(source[i])))
            bad = "can not move directory into itself";

at line ~207 in builtin-mv.c.


If the source isn't a prefix of the destination things works as expected,

    $ git mv README renamed-README
    $

- Fredrik