Option for pm-update/pm-updatecode to remove existing files before installing new ones

It would be useful to have an option for pm-update/pm-updatecode to remove the existing module/theme files before extracting the new ones.

• Many modules go through file name changes and can leave stray files lying around that can either just a) confuse the site maintainer or, worse yet, lead to bugs in the site.
• On the flip side, sometimes dependencies are copied within the module's directory structure and would cause the module to break were they to suddenly disappear, e.g. jQuery_UI.
• Lastly, because many revision management systems leave system files within the directory structure, care has to be made to not accidentally delete the wrong files.

So what I propose is an option, --remove-files, that would remove all files within the directory with the exclusion of common known files, e.g. (pseudocode):

$count = 1;
while (system("rm -f {modulepath}" . str_repeat('/*', $count))) {
  $count++;
}

The above code works because the '-f' flag to the UNIX 'rm' command forces files to be deleted but does not descent into directories, and because using the '*' file selector ignores files which start with a period, e.g. ".svn", ".git", etc. It does open a problem with CVS as those directories would have their files removed, so obviously the code would probably work better in PHP with some proper filtering of the directory tree prior to file deletion.

Icing on the cake would be another option named --dont-remove which accepted a list of filenames/paths which were not removed, e.g. to account for unusual revision management tool system files.