Linking subreports in iReport so they also work in Jasper server

Question

Using iReport v4.0.1 with Jasperserver v4.1.0 I'm trying to find a syntax for linking subreports to the main report that lets me test it in iReport then deploy to the server through the repository browser.

The default syntax for sub-reports in iReport for the subreport expression is something like

$P{SUBREPORT_DIR} + "mySubReport.jasper"

When you deploy this from iReport it's smart enough to pick this up and suggest changing it to

"repo:mySubReport.jrxml"

and to then deploy all subreports to the Resources folder of the main report.

That's great, but unfortunately it then edits the file in iReport to save this change which means you can no longer run the report in iReport without manually re-editing all the sub-report expressions - this makes the process of testing and deploying to the server really painful, particularly when there are multiple sub-reports in a report.

I thought I could at least set the value of $P{SUBREPORT} to be "repo:" or "My\local\filepath" so that at least I'd only have one place to change it, but the compiler doesn't like that.

Is there an alternative structure or an expression that will resolve to repo:*.jrxml or My\local\filepath*.jasper correctly depending on where you're running the report from?