Shortening dest file path creation

Using this substring syntax: DEST_FILE=${SRC_FILE#$SYNCROOT}
test_syncroot: putting path to test in a variable

That makes it easy to test other syncroots. If you choose a syncroot
with a space, the test will fail. That's a big bug.
Download Action

A new feature requiring lftp installed. It assembles an lftp mirror
command to download all changes from the FTP server into your current
working tree.

It deletes untracked files. Ideas how to tackle this:
- Accept it. Download is supposed to mirror. (I guess not.)
- Check for untracked files and throw an error before downloading. (My
  favourite.)
- Stash everything away and restore it after downloading. (Does too
  much. Could confuse. Could create a conflict.)