Fix lost options and args

I noticed a bug a while back but didn't have much time to track it down at the time.  When using `-rHEAD`, I noticed that `svnwrap` would happily put just the `-r` on the command line.  And while looking at the code to fix that problem, I noticed that the `.append()` statement was outside the while loop, which meant that commands like `svn st -uv` would lose the all but the last option.  This PR fixes both of those issues.