This commit changes how rebar determines which apps have been
updated, added and removed from a release during appup generation.
Rather than use app files it now determines this from the rel file
in each version of the release. In addition it fixes a bug reported
on the mailing list when generating appups when an application has
been added or removed from either release.
To further support OTP releases I have added support for generating
application appup files. These include instructions that systools uses
to generate a relup file which contains the low level instructions
needed to perform a hot code upgrade. My goal with this module is to
produce "good enough" appup files or at least a skeleton to help one get
started with something more complex. If an appup file already exists for
an application this command will not attempt to create a new one.
Usage:
$ rebar generate-appups previous_release=/path/to/old/version
Generally this command will be run just before 'generate-upgrade'.
