We need to build multiple apps from the same code source, we have experimented with creating mulitple xdk files within the same project folder (eg app1.xdk, app2.xdk...etc), and it seems to be working fine. This means the "plugins" and "www" folders are shared across all apps, but we can assign different build settings for each app, including app id, etc...
Is there any reason why we should not do this, or is there any known issues with this set up?
Interesting solution. This will work as long as you are keeping the majority of the build settings identical between projects. But it sounds hazardous if you don't play close attention.
I would recommend using links (symbolic links might work, hard links should definitely work) from unique projects to a common source project. You might be able to do this just by linking to the "source directory" (normally named www) from each active project to the common source project. That way the source code changes you make will show up in each project, but the other project components, such as the project.xdk files, the plugins directory, etc. will be unique and will not interfere.
Symbolic and hard links to exist on Windows systems, if you are using Windows, they just are not widely publicized. This article provides lots of good info on them for Windows > http://www.howtogeek.com/howto/16226/complete-guide-to-symbolic-links-symlinks-on-windows-or-linux/. Microsoft actually uses them quite heavily in Windows 8+ systems. For example, cd to \Users and type dir /ah to see something like this:
C:\Users ( ) >dir /ah Volume in drive C is C-drive Volume Serial Number is 9A3F-2886 Directory of C:\Users 08/22/2013 07:45 AM <SYMLINKD> All Users
09/25/2014 09:26 AM <DIR> Default 08/22/2013 07:45 AM <JUNCTION> Default User 08/22/2013 08:34 AM 174 desktop.ini 1 File(s) 174 bytes 3 Dir(s) 20,197,154,816 bytes free
Likewise, cd to your home directory (cd %UserProfile%) or to the root of your system drive (cd \) and do the same experiment to see other links.