For now, this is just a proof of concept; would make sense to add a lot of things, such as quick access to invoking rebar itself (with approproate code reloading), as well as an eunit-aware version so that tests could be run interactively.
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'.
To support OTP release upgrades I have added support for building upgrade packages. Support for this is included in the rebar_upgrade module, specifically generate_upgrade/2. It requires one variable to be set on the command line 'previous_release' which is the absolute path or relative path from 'rel/' to the previous release one is upgrading from. Running an upgrade will create the needed files, including a relup and result in a tarball containing the upgrade being written to 'rel/'. When done it cleans up the temporary files systools created. Usage: $ rebar generate-upgrade previous_release=/path/to/old/version This also includes a dummy application that can be used to test upgrades as well as an example. Special thanks to Daniel Reverri, Jesper Louis Andersen and Richard Jones for comments and patches.
Erroneously put rebar_pre_script at the end of the app_dir modules list in the previous commit.