This makes uploading a lot of attachments somewhat faster, because
the user does not need to wait for a long website refresh after each
upload. Still probably somewhat slow, since ikiwiki has to run for each
upload.
More importantly, this opens the door for integration of things like
the jquery file upload interface, which allow drag-n-drop and multiple
file uploads to be queued and then ran.
It uses rcs_commit_staged, which leaves out tla and mercurual which lack
that, but since rename, remove, autoindex, etc also use that, I think it's
fine for attachments to also depend on it.
The attachment list is currently broken; it does not look in the holding
area yet, and its links to the attached files won't work since they're not
yet in the wiki. previewing is also currently broken.
Work sponsored by TOVA.