Allowing user to customize groovysh prompt

Took this change beyond the requested change. I did the following actions:

1. Changed the renderPrompt() method to be public
2. Refactored renderPrompt() to call a private method called buildPrompt().

The buildPrompt() method builds the groovy shell command prompt name in 1 of 3 ways:

1. Checks the groovysh.prompt property passed into groovysh script. -Dgroovysh.prompt="hello"
2. Checks an environment variable called GROOVYSH_PROMPT. export GROOVYSH_PROMPT
3. If no value is defined returns the default groovy shell prompt.

The code will always assume you want the line number in the prompt. To not have the numbers in the prompt, you
can simply override the renderPrompt() method.

If anyone has questions, comments or concerns about how I implemented the change or would like to see it implemented differently let me know.

Thanks,
John

Thank you for this patch, it is exactly what I want.

By the way, a diff would be better than just the raw file.

Great patch, it solves part of my problem! My intent is to use GroovySh inside an Eclipse debug/launch configuration to have a more convenient grails dev environment for simple tests and script running/debugging. I got everything running except that groovsh fails to accept input probably because some conflicts between the jline DLL stuff and eclipse. My workaround is to set "-Djline.terminal=jline.UnsupportedTerminal" Now GroovySh works inside Eclipse console but this ends in a prompt like this:
[1mgroovy:[0m000[1m>[0m
Customizing the prompt helps here.

However what I am really looking for is to preserve as much functionality as possible from Groovysh without using jline (or at least jline's native code). As jline was added later to groovysh it might be useful to preserve what was there before as a lightweight alternative for such environments? Any thoughts about this? Where would the best place to start... Replace InteractiveShellRunner? put an abstraction layer on top of ConsoleReader? Are there more dependencies on AnsiRenderer except the prompt? Any hint/comment would be welcome.

Not sure how others think about this but in my opinion having Groovysh available in a debugging environment would be an awesome feature to debug Groovy or in my case grails scripts.

Setting -Djline.terminal=jline.UnsupportedTerminal is not a workaround, it is the way you configure JLine for unsupported terminal interfaces, like with Eclipse. IMO it is pointless to use Groovysh w/o JLine. If you don't want or can't use the advanced console features, then configure the UnsupportedTerminal.

Jason thanks for commenting. I consider this a workaround as it is a means to make something behave as it is supposed to do. I do not claim that there is somewhere a bug. Digging deeper into the code and getting a better understanding how Grovysh works I agree that it does not make much sense to replace jline with something else in pure Java. However there might be possibilities to make jline work in a debugger... But this is something that does not belong to this issue tracker any longer (we have left the original issue anyway...) Sorry for that and thanks for sharing ideas. I still consider proper terminal support in a debugger a very useful feature for Groovysh.

You still have basic readline support when you set the terminal to unsupported, which is imo still proper. Not sure what you want it to do when its running in an IDE's environment. Your integration needs to tell jline how to behave, or install your own custom Terminal implementation to handle the environment.