We've got several large obsolete branches in our Perforce depots. What I would
like to do is something like:

p4 obliterate -y //depot/obsolete_branch/...

But these branches contain on the order of 20,000 files and I know that
obliterate is a costly operation which includes lots of file locking. This
makes me concerned that the action above would effectively "shut down" our
server for a VERY long time.

I've read some old documents about doing these kind of operations by editing the
checkpoint and then restoring from the checkpoint. This seems more efficient,
but I'd be concerned about the scope of the edits involved and the possibility
for fairly catastrophic error.

Any suggestions? I'd be especially interested to hear from anyone who's done a
"huge" obliterate.