[PATCH] Add '--drop-all-empty-revs' to svndumpfilter include/exclude

Hi,

Recently, I had a chance to look at a dump file with lot of empty
revisions. The dump file was taken by syncing a sub-directory of a
remote repository using svnsync. I decided to remove all the empty
revisions from the dump file. But 'svndumpfilter include/exclude
--drop-empty-revs' was of no use, since it removes only the revisions
emptied by filtering process.

When I checked with the issue tracker, there is already one open
issue[1] for this problem. There was a mailing list discussion[2] which
proposes to change the behavior of '--drop-empty-revs' to drop *all* the
empty revisions instead of removing the ones emptied by filtering process.

As cmpilato said in the thread, the change in behavior would break our
compatibility promises and new command-line option
'--drop-all-empty-revs' would help to resolve this issue.

This patch introduces a new option '--drop-all-empty-revs' to
svndumpfilter include/exclude.

Attached the patch and log message. Please share your thoughts.

[1] http://subversion.tigris.org/issues/show_bug.cgi?id=3681
[2] http://svn.haxx.se/dev/archive-2010-07/0083.shtml

Thanks & Regards,
Vijayaguru