.. _variables:
+Updating regression tests
+~~~~~~~~~
+
+Changes in |GROMACS| that require changes in regression-tests are notoriously hard,
+because a merge request that tests against the non-updated version of the
+regression tests will necessarily fail, while updating regression tests while
+the current change is not integrated into master, might cause other
+merge request pipelines to fail.
+
+The solution is a new regression-test branch or commit, uploaded to gitlab.
+Then set that regression test branch with REGRESSIONTESTBRANCH or
+the specific commit with REGRESSIONTESTCOMMIT when
+running the specific pipeline that requires the regressiontest-update.
+See below on how to set variables for specific pipelines.
+
Variables
~~~~~~~~~
patch to the base Docker images to include the dependency to reduce
pipeline execution time.
+ REGRESSIONTESTBRANCH
+ Use this branch of the regressiontests rather than master to allow for
+ merge requests that require updated regression tests with valid CI tests.
+
+ REGRESSIONTESTCOMMIT
+ Use this commit to the regressiontests rather than the head on master to
+ allow for merge requests that require updated regression tests with
+ valid CI tests.
+
+
.. todo:: Define common variables.
``BUILD_DIR``, ``INSTALL_DIR``, ``CACHE_FALLBACK_KEY``, ...
+
+Setting variables
+~~~~~~~~~
+
+Variables for individual piplelines are set in the gitlab interface under
+``CI/CD``→``Pipelines``. Then chose in the top right corner ``Run Piplelines``.
+Under ``Run for``, the desired branch may be selected, and variables may be set
+in the fields below.
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