Simple command-line Regex file renamer

Usage:
  rxmv [-x] regex formatString file(s)

This program will match each of the files with the given regex, then substitute into the given formatString
to generate the new filename.

If the '-x' flag is passed, the program will rename the files.  
If not, it will print out a report of what the renaming would look like.


Regular Expressions are as understood by Boost:
http://www.boost.org/doc/libs/1_53_0/libs/regex/doc/html/boost_regex/syntax.html

formatString is also as understood by Boost:
http://www.boost.org/doc/libs/1_42_0/libs/format/doc/format.html#syntax


Example:
Let's say you copied a bunch of songs from a buddy of yours.  But, this ignorant jackass uses some cockamamie naming scheme for his files.  Or, worse, lets his files be named automatically by like iTunes or something.  Let's take a look!

[~]$ cd new-gems
[~/new-gems]$ ls
10 Cross.mp3                      5 I Dig You.mp3                   
1 Love Crushing.mp3               6 Mr. Bad.mp3
2 Say The Word.mp3                7 You're So Much.mp3
3 (I Feel Like An) Astronaut.mp3  8 Bonework.mp3
4 Deep Blue.mp3                   9 Spot.mp3


Unacceptable!  You want to bring these tracks in line with the Naming Convention of the People.  Run rxmv in report mode to try out a name fix:

[~/new-gems]$ rxmv '(\d+)\s*(.*)\.(...)' '%1$02d - %2%.%3%' *
10 Cross.mp3 --> 10 - Cross.mp3
1 Love Crushing.mp3 --> 1 - Love Crushing.mp3
[...]

Looks good, we've gotten rid of the asinine lack of zero-padding on the numbers, and we've added in dash separators.  Here's how that worked:

(\d+)\s*(.*)\.(...)   means:
* match some number of digits and remember them
* skip all whitespace after these digits
* match any characters before the last period and remember them
* skip over the last period
* match three characters at the end and remember them

%1$02d - %2%.%3%  means:
* Print the first thing we remembered (digits), and zero-pad them to a width of two
* Print a space, then a dash, then another space
* Print the second thing we remembered (the song title), as is.
* Print a period
* Print the third thing we remembered (the file extension), as is.



Since that looked good, now run the command to rename for real:
[~/new-gems]$ rxmv -x '(\d+)\s*(.*)\.(...)' '%1$02d - %2%.%3%' *
[~/new-gems]$ ls
01 - Love Crushing.mp3               06 - Mr. Bad.mp3
02 - Say The Word.mp3                07 - You're So Much.mp3
03 - (I Feel Like An) Astronaut.mp3  08 - Bonework.mp3
04 - Deep Blue.mp3                   09 - Spot.mp3
05 - I Dig You.mp3                   10 - Cross.mp3


Boom.  Done.  See how nice that looks?  Now you can share these gems with your subjects.



To compile, you're going to need the following:

1) A compiler that understands C++11.
2) Boost's regex, format, and filesystem libraries

The actual code should run on any system, but build/compilation details will vary based on your compiler and system.
If your system has CMake, that should work. Or you can try a command line like this:
```
c++ --std=c++0x -g rxmv.cpp -lboost_regex -lboost_filesystem -lboost_system -o rxmv
```