Put explicit length constraints on new target names:

    0 < len(name) < some max value

Consider making -x interact with -c and -g

Check all examples in the doc.

Test on Windows and Linux.


Documentation
-------------


- Get rid of the toggles and their associated docs having to do with
  resetting options to their default state.  No longer needed now that
  we're not allowing option-target pairs.

- -v now continues after displaying results.  This allows it
   to go into log outputs.

- Note that multiple items sharing the same sequencing key (ctime,
  size) will be ordered alphabetically within that key.

- Change -f description to indicate that it will merely rename (not
  remove) the existing target.

- Document -S (Default: ".backup")

- Note limit of total new filename length is 255.

- Document -w linelength option. Default: 80.  Program determines
  min output length. ONLY for error and info output (which can
  be long).  Ordinary program output like usage and version info
  ignores this.  If capturing for log/analysis, set this very wide.

- Get rid of references to option-target pairs.  Note that from the
  first non-option string forward, everything is understood to be
  a filename even if it is in -option format.

- Document -R rensep - single char

- Document, all the stat-based sequences as well as alpha asc- desc-

- Note importance of doing -d last, right before filename args to
  get most current state of prog.

- Note that '\' may itself have to be escaped on the shell command line.

- Note the -E only applies during renaming operations.  Other errors will
  halt program.

- Changed option -1 to -G

- -r  =something -> entire target name is replaced by "something"
  -r  something= -> "something" is removed from the target name

- Note that twander can be used as a GUI frontend for tren.

- Note the use of docutils/resturctured text in producing the docs.

- Document -P escape single char.

- Changed option -l to -L.

- Document overlapping renames:

    - Because of overlapping substitutions

        Note specific multi-rename semantics disjoint, overlapping, reduced
        string length.

    - Because of filename collisions

       Note the potential problem of:

        Rename: x -> x1 causes existing to be renamed x1.backup
   
        Now a rename of x1 -> z1 still works *but we're renaming a different file* (originally x)

        Do this repeatedly and you'll wipe out all but the last file and backup

- Backups can be backed up:

  foo.backup.backup.backup...

- Note that -q clobbers ALL informational output, even during test
  runs: -qt does not make sense

- The whole name/extension distinction has been removed.  The eliminates the following options:

   -a
   -b
   -e
   -L