gitlab: don't run CI jobs in forks by default

To preserve CI shared runner credits we don't want to run
pipelines on every push.

This sets up the config so that pipelines are never created
for contributors by default. To override this the QEMU_CI
variable can be set to a non-zero value. If set to 1, the
pipeline will be created but all jobs will remain manually
started. The contributor can selectively run jobs that they
care about. If set to 2, the pipeline will be created and
all jobs will immediately start.

This behavior can be controlled using push variables

  git push -o ci.variable=QEMU_CI=1

To make this more convenient define an alias

   git config --local alias.push-ci "push -o ci.variable=QEMU_CI=1"
   git config --local alias.push-ci-now "push -o ci.variable=QEMU_CI=2"

Which lets you run

  git push-ci

to create the pipeline, or

  git push-ci-now

to create and run the pipeline

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220526110705.59952-6-berrange@redhat.com>
[AJB: fix typo, replicate alias tips in ci.rst]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20220527153603.887929-33-alex.bennee@linaro.org>

2 files changed, 47 insertions, 0 deletions

diff --git a/.gitlab-ci.d/base.yml b/.gitlab-ci.d/base.yml
index 4f091d5aad..f334f3ded7 100644
--- a/.gitlab-ci.d/base.yml
+++ b/.gitlab-ci.d/base.yml
@@ -28,6 +28,10 @@
     - if: '$QEMU_JOB_ONLY_FORKS == "1" && $CI_PROJECT_NAMESPACE == "qemu-project"'
       when: never
 
+    # Forks don't get pipelines unless QEMU_CI=1 or QEMU_CI=2 is set
+    - if: '$QEMU_CI != "1" && $QEMU_CI != "2" && $CI_PROJECT_NAMESPACE != "qemu-project"'
+      when: never
+
     # Avocado jobs don't run in forks unless $QEMU_CI_AVOCADO_TESTING is set
     - if: '$QEMU_JOB_AVOCADO && $QEMU_CI_AVOCADO_TESTING != "1" && $CI_PROJECT_NAMESPACE != "qemu-project"'
       when: never
@@ -59,5 +63,10 @@
     # an earlier criteria
     #############################################################
 
+    # Forks pipeline jobs don't start automatically unless
+    # QEMU_CI=2 is set
+    - if: '$QEMU_CI != "2" && $CI_PROJECT_NAMESPACE != "qemu-project"'
+      when: manual
+
     # Jobs can run if any jobs they depend on were successfull
     - when: on_success
diff --git a/docs/devel/ci-jobs.rst.inc b/docs/devel/ci-jobs.rst.inc
index 0b4926e537..9118a61a17 100644
--- a/docs/devel/ci-jobs.rst.inc
+++ b/docs/devel/ci-jobs.rst.inc
@@ -28,6 +28,32 @@ For further information about how to set these variables, please refer to::
 
   https://docs.gitlab.com/ee/user/project/push_options.html#push-options-for-gitlab-cicd
 
+Setting aliases in your git config
+----------------------------------
+
+You can use aliases to make it easier to push branches with different
+CI configurations. For example define an alias for triggering CI:
+
+.. code::
+
+   git config --local alias.push-ci "push -o ci.variable=QEMU_CI=1"
+   git config --local alias.push-ci-now "push -o ci.variable=QEMU_CI=2"
+
+Which lets you run:
+
+.. code::
+
+   git push-ci
+
+to create the pipeline, or:
+
+.. code::
+
+   git push-ci-now
+
+to create and run the pipeline
+
+
 Variable naming and grouping
 ----------------------------
 
@@ -98,6 +124,18 @@ Contributor controlled runtime variables
 The following variables may be set by contributors to control
 job execution
 
+QEMU_CI
+~~~~~~~
+
+By default, no pipelines will be created on contributor forks
+in order to preserve CI credits
+
+Set this variable to 1 to create the pipelines, but leave all
+the jobs to be manually started from the UI
+
+Set this variable to 2 to create the pipelines and run all
+the jobs immediately, as was historicaly behaviour
+
 QEMU_CI_AVOCADO_TESTING
 ~~~~~~~~~~~~~~~~~~~~~~~
 By default, tests using the Avocado framework are not run automatically in