update github tutorial/howto for recent changes in the development workflow

doc/src/Howto_github.txt

@@ -254,20 +254,53 @@ them, or if a developer has requested that something needs to be changed
 before the feature can be accepted into the official LAMMPS version.
 After each push, the automated checks are run again.
 
+[Labels]
+
+LAMMPS developers may add labels to your pull request to assign it to
+categories (mostly for bookkeeping purposes), but a few of them are
+important: needs_work, work_in_progress, test-for-regression, and
+full-regression-test. The first two indicate, that your pull request
+is not considered to be complete. With "needs_work" the burden is on
+exclusively on you; while "work_in_progress" can also mean, that a
+LAMMPS developer may want to add changes. Please watch the comments
+to the pull requests. The two "test" labels are used to trigger
+extended tests before the code is merged. This is sometimes done by
+LAMMPS developers, if they suspect that there may be some subtle
+side effects from your changes. It is not done by default, because
+those tests are very time consuming.
+
+[Reviews]
+
+As of Summer 2018, a pull request needs at least 1 approving review
+from a LAMMPS developer with write access to the repository.
+In case your changes touch code that certain developers are associated
+with, they are auto-requested by the GitHub software.  Those associations
+are set in the file
+".github/CODEOWNERS"_https://github.com/lammps/lammps/blob/master/.github/CODEOWNERS
+Thus if you want to be automatically notified to review when anybody
+changes files or packages, that you have contributed to LAMMPS, you can
+add suitable patterns to that file, or a LAMMPS developer may add you.
+
+Otherwise, you can also manually request reviews from specific developers,
+or LAMMPS developers - in their assessment of your pull request - may
+determine who else should be reviewing your contribution and add that person.
+Through reviews, LAMMPS developers also may request specific changes from you.
+If those are not addressed, your pull requests cannot be merged.
+
 [Assignees]
 
-There is an assignee label for pull requests. If the request has not
+There is an assignee property for pull requests. If the request has not
 been reviewed by any developer yet, it is not assigned to anyone. After
 revision, a developer can choose to assign it to either a) you, b) a
-LAMMPS developer (including him/herself) or c) Steve Plimpton (sjplimp).
+LAMMPS developer (including him/herself) or c) Axel Kohlmeyer (akohlmey).
 
 Case a) happens if changes are required on your part :ulb,l
 Case b) means that at the moment, it is being tested and reviewed by a
 LAMMPS developer with the expectation that some changes would be required.
 After the review, the developer can choose to implement changes directly
 or suggest them to you. :l
-Case c) means that the pull request has been assigned to the lead
-developer Steve Plimpton and means it is considered ready for merging. :ule,l
+Case c) means that the pull request has been assigned to the developer
+overseeing the merging of pull requests into the master branch. :ule,l
 
 In this case, Axel assigned the tutorial to Steve:
 
@@ -381,3 +414,6 @@ Furthermore, the naming of the patches now follow the pattern
 "patch_<Day><Month><Year>" to simplify comparisons between releases.
 Finally, all patches and submissions are subject to automatic testing
 and code checks to make sure they at the very least compile.
+
+A discussion of the LAMMPS developer GitHub workflow can be found in the file
+"doc/github-development-workflow.md"_https://github.com/lammps/lammps/blob/master/doc/github-development-workflow.md