SVN::S4

I'd find it useful to have the following s4 commands.

• Sometimes I want to "viewify" my working copy without changing the revision that I'm at.
• Effectively, this is s4 update -rX (where X is the current revision of the working copy).
• There are some corner cases that may need to be worked out here.

• Occasionally, I have a s4 working copy that I'd like to move back to a normal svn working copy.
• Effectively, this is removing all view commands from a Project.viewspec, updating to the current revision of the working copy, and restoring the Project.viewspec.
• You might need to require an s4 scrub before allowing the s4 unview operation.

I can provide more details about and motivations for this feature request, if desired.