We have several exists JIRA projects set up on our system and recently we installed the greenhopper plugin (which looks awesome btw). Before we had the greenhopper plugin we were still doing agile development and have issue types called "Story" and "Epic", we also have fields in these such as business priorty and points.
I'd really like to make use of the story points functionality to be able to easily see effort in an iteration however looking at the documentation it seems to do this I have to use the "Story Points" field that greenhopper created.
1) Is it possible to tell greenhopper to use my existing points field for story points?
2) if not, is it possible to easily migrate the data in my current field to the new field type?
Obiviously I don't really fancy going through all our stories and manualy moving the points across!
I don't think you have to use the Story Points field that Greenhopper created. It exists as part of the GH Scrum Template introduced years ago to kick start teams that were new to GH and minimize configuration required out of the box. You had to add all these things in manually previously and they made it easier by creating the standard issue types, points, field, rank, etc. people typically wanted for Agile Development.
This from the documentation:
If you are using the 'Scrum' template, custom statistics called Story Points and Business Value will be created for you automatically.
This means that if you aren't, you need to either configure your project to use that field OR create your own.
You should be able to use your existing story points field, but you might need to do some clean up in your Custom Fields section so that you don't have two fields called "Story Points", or what have you, that essentially do the same thing.
I don't believe the story points field is any special type of field, it's just a numeric field called Story Points that you can recreate or use your existing points field. That field would have to be added as a Statistics field to be able to chart progress in points on the burndowns and setup any statistical markers, column constraints or other tidbits that rely on statistics fields.
I can't think of a reason why you can't use your own field for points, but maybe someone else can chime in with a counter. I'm pretty sure that field is just there to make life easier on new admins.
I can't think of a way to easily migrate the data though. I know you can do so with the workflow, using a post function to copy a field value from one field to another, but that's at the issue level, not sure how you would do that in bulk.
my 2 cents.
FYI the new Rapid Board seems hard coded to Story Points, so configuring statistics won't help you if you want to use the Rapid Board, you'd have to do some migration. Starting a new thread for that:https://answers.atlassian.com/questions/44682/what-is-the-migration-path-to-the-rapid-board-from-time-tracking-to-story-points