vcsh: don't allow `clone` to choke on filenames with spaces

By replacing the "for" loop with a "while" loop, it is easy to read
line-oriented output without worrying about spaces. However, now the
loop executes in a subshell, and VCSH_CONFLICT won't be available in
the parent shell. In this case, a trivial, portable solution is to
have the comparison as the last command in the subshell.