OVERVIEW
========
"autorelease" is a set of scripts and enhancements to the
versions-maven-plugin (to be upstreamed if accepted) that enable to
streamline the release process of ODL, and to perform the process
before any GIT TAG is actually pushed to the central repo as well and
nexus artifacts is not deployed till the whole process is done.

SCRIPTS EXPLANATION
================
- "autorelease" is the driver script that goes over the list of
 repositories and perform a localrelease on each of them. The script
 first all runs the versions-maven-plugin to make sure all the
 artifacts belonging to "org.opendaylight*" are updated to the latest
 released version, that means for example that after yangtool is build
 and released locally, controller project will transform all the
 "-SNAPSHOT" dependencies from yangtools to be the just released
 yangtools artifacts, so the release process can work happily.

- "localrelease" is in charge of performing the release of a single
  project, it assumes that there are no -SNAPSHOT dependencies to
  external projects, this should be guaranteed by the fact the
  "autorelease" runs the project based on the order of dependency and
  that the "versions-maven-plugin" correctly detect the SNAPSHOT
  dependencies and changes them to the just released versions.

- "pushrelease" is the script supposed to be run at the end of the
  release process so the GIT tags for the release just performed are
  pushed out and the released artifacts that has been deployed local
  are actually upstreamed to the central nexus

BASIC WORKFLOW
==============
A sample workflow goes like this:

1) Release a list of projects, if the repo names are not fully
qualified they are assumed to be relative to:
"https://git.opendaylight.org/gerrit/"

./autorelease --repositoryList "yangtools.git controller.git openflowjava.git"

2) If the process in step #1 completes fine (will take a while) you
can push out the release using:

./pushrelease --repositoryList "ssh://git.opendaylight.org:29418//controller.git ssh://git.opendaylight.org:29418//yangtools.git ssh://git.opendaylight.org:29418//openflowjava.git" --mavenDeployTargetURL "https://nexus.opendaylight.org/content/repositories/opendaylight.release/" --mavenDeployTargetID "opendaylight.release"

This last step assume that you can deploy tags to the GIT repositories
as well be able to upload to nexus.

THEORY OF OPERATION
===================
The release performed by auto-release wants to be not intrusive into
the day-to-day job of the GIT repositories, so let assume you start
from a situation where you have the repositories like:

  [master]
  -----------------------------------------------------------------> (yangtools)
                                                                   t
  [master]
  -----------------------------------------------------------------> (controller)
                                                                   t
  [master]
  -----------------------------------------------------------------> (ovsdb)
                                                                   t

 ...... ETC.

  at the time and date when the release is performed the branch
  situation will look like this:


  [master]
  -------------------+---------------------------------------------> (yangtools)
                     |                                             t
                     \---[autorelease-branch-v20140430040302_57eda02]

  [master]
  -------------------+---------------------------------------------> (controller)
                     |                                             t
                     \---[autorelease-branch-v20140430042302_23dfe02]

  [master]
  -------------------+---------------------------------------------> (ovsdb)
                     |                                             t
                     \---[autorelease-branch-v20140430051302_ff6aa02]

The release script would have just branched out from master and would
have applied only the necessary patch to remove the -SNAPSHOT
dependencies as well to generate pom for the released artifacts
(without -SNAPSHOT at the end). The process would have not changed
master branch at all. Clearly given there are no changes to master
subsequent releases in order to ensure that don't create conflicting
release numbers, and release numbers that are incremental, will get a
build qualifier appended which is in the form of:
      v{year}{month}{day}{hour}{min}_{git short commit ID for HEAD}


CAVEATS
=======
1) The script at the moment release out of master, but can be enhanced
to work on any stable branch
2) The modified maven-versions-plugin currently if need to replace a
variable in a pom, replace it with the expanded value and doesn't
update the property, this is a bug and need to be fixed