changes to the LAMMPS development workflow

Hello everybody!

This is for those of you who stay up-to-date or contribute to LAMMPS via
Git or SVN. As of today, we are making some changes to the Git/SVN
public repos that host LAMMPS for download or development purposes. In
particular, how changes are integrated into LAMMPS that users provide as
git pull requests.

The official home of public LAMMPS development is now on GitHub at
https://github.com/lammps/lammps. This Git repository is kept
synchronized with the internal SVN server at Sandia.

NOTE: the previously advertised LAMMPS git and svn repositories on
git.lammps.org, svn.lammps.org and bitbucket.org are now deprecated,
may not be updated, and may go away at any time.

Subversion access to the LAMMPS development is provided through
a git-to-svn service provided by GitHub. This is incompatible with
previous subversion checkouts, so you’d have to make a new checkout.
Updated descriptions on how to check out the LAMMPS development
repository with git and svn have been posted to
http://lammps.sandia.gov/download.html

Both git and subversion now provide 3 different branches that you can
follow to stay up-to-date.

stable : this branch is updated with every stable release
unstable : this branch is updated with every patch release
master : this branch continuously follows ongoing development

If you want to contribute new features or bugfixes to LAMMPS, you
can file pull requests at: https://github.com/lammps/lammps/pulls
These pull requests will be merged into the “master” branch and
thus should be kept up-to-date, in case GitHub indicates there are
problems with merging. Pull requests will also be subject to a
simple integration testing, e.g. it will be checked, if the code
compiles with a selection of settings and a code review. You can
see, which LAMMPS developer is currently working on your submission
in the “Assignees” field, and you can also review the status of
the automated checks and the code review. People submitting pull
requests or proposing to implement new features will receive an
invitation to collaborator status in the LAMMPS GiHub project.

You may still submit changes by e-mailing them to one of the LAMMPS
developers directly. The “lammps-icms” branch, that was previously
used for merging pull requests will no longer be maintained and
deleted after all its additional features have transferred into LAMMPS
itself or the “lammps-testing” or “lammps-packages” repositories.

All LAMMPS patch releases will now receive a tag in the format
“patch_” to simplify makeing comparisons between
releases and also for updating the “stable” and “unstable”
branches. All patch releases will receive a more thorough automated
regression testing and the coverage of the testing will be
significantly expanded in the coming months.

Please be a little patient, while we are transitioning and let us
know, if there are any problems that need to be addressed, or if
you have suggestions for further improvements of the process.

Axel Kohlmeyer, Richard Berger, Steve Plimpton