groovy cannot find startGroovy if the groovy executable is a symlink

A lot of people like to create symlinks to executable binaries or scripts. For example, many linux systems use the alternatives system to symlink

/usr/bin/progname -> /etc/alternatives/progname -> /path/to/progname

Currently, groovy does not support this option. If I have:

$ ls -l /home/greg/bin/groovy
lrwxrwxrwx 1 greg greg 40 2009-02-22 22:49 /home/greg/bin/groovy -> /home/greg/opt/groovy/current/bin/groovy

And I try to run:

$ groovy -e 'print("HELLO GROOVY")'

1. 1. 1. I get:
         .: 28: Can't open /home/greg/bin/startGroovy

A simple fix would be (adapted from the jruby startup script):
------------------------------
1c1
< #!/bin/sh
—
> #!/bin/ksh
15a16,29
> get_dirname()
>

>
17c31
< DIRNAME=`dirname "$0"`
—
> DIRNAME=`get_dirname $0`
--------------------

The above was tested in bash, dash and pdksh.

Ideally, the same patch would be applied to groovyc and groovysh as well