undo + mv => unexpected

[Matthew Dillon]

:`undo -i' seems to track the wrong file after mv, see below.
:Contents of file is correct;
:`hammer history' seems correct.
:
: -thomas

    Ok, I figured out what is going on here.  What is happening is
    that doing a 'rename' does not modify the file, so no new history
    is being added.  A file create modifies the file, of course.  A 'rm'
    will also modify the file because it drops the hardlink count by 1,
    but a 'mv' does not have to modify the file.

    The undo program fetches the history internally in order to get the
    most recent transaction id, and then tries to open the file using
    that transaction id before printing the history.

    however, when you've mv'd the file, that transaction id will be prior
    to when the mv was made, so undo's attempt to open the file using
    the new name will fail.

    Pretty cool!

    For the moment, so things work somewhat as expected, I will adjust
    the undo program to attempt to open the 'current' file under its new
    name if it is unable to open the file via the transaction id.  That
    will help display the history, but the diff feature will probably still
    fail.

    So undo isn't going to be perfect, it will not be able to access the
    file for any period prior to it being renamed unless you also know
    the original name (prior to the mv). If you do know that name then you
    are golden.

						-Matt