BCS 746-000808

Prior to this change the integration stop when one of the projects had
already the latest ref of gitlab-ci in to submodule.

The integration branch was reused even if there where new commits on the
target branch, which could lead into reverting some changes.
This adds a check, if the existing integration branch is directly based
on the target branch and deletes it if not.

Rename variable JENKINSGUF_SSH_PRIVATE_KEY / SSH_PRIVATE_KEY to
GITLAB_PRIVATE_KEY on this occasion, because it contains a private key
that was generated exclusively for this use case. The according public
key has been added as a deploy key in GitLab to all repositories that
this repository needs access to.

Add more detailed documentation concerning this configurationdirectly in
the gitlab-ci files.

The deploy_gitlab_ci now creates the integration commit and branch in
each passed subproject and create an integration commit in the manifest
containing all these new revisions.
A build is then triggered on this commit to test the functionality.

Split the update_submodule functions to reuse them in different ways.
Remove some previously used files.

BCS 746-000740

As all projects are commited in the same branch the 'up-to-date' check
may not only check if the first parent commit points to the
master/dunfell branch. Now it is needed to loop through the history
until the integration branch's commit is found.

On fail a message is displayed which merge request needs to be
retriggered manually. This can now also be the 'parent'-MR that
triggered the complete chain.

The check job is used pipeline again.

The retrigger job also looks in the .gitlab-ci project for check jobs to
retrigger.

Allow deploy_gitlab_ci to change multiple projects at once.
Use it to create integration branches and merge requests in all
projects.

Add a python file to generate a job yml from jinja2 template.
Add a template for the jobs to trigger. These execute the actual
integration in all 'subprojects'.
Create the yml file in the deploy job and trigger it in a new trigger
job.

Add update gitlab-ci file with function to adapt the include ref to a
given revision.
Add a 'pre-commit-hook' to the update-submodule function.
Adapt deploy_gitlab_ci to use these to update the include statement in
the base project .gitlab-ci.yml to use the same ref as the submodule
is set to.

BCS 746-000646

This allows to increase the verbosity. Add --verbose in .gitlab-ci.yml
when the python script is called to view the output in the jobs log.

Fix pylint errors introduced with new pylint version:
* unspecified-encoding: explicitly set encoding when opening a file
* assigning-non-slot: use "set_reference()" function instead of assigning
  a value to the "reference" attribute
* unused-variable: remove "e" variable on exceptions when not referenced

If integration branch already existed and had to be replaced, the new
commit was accidentally pushed on top of the already existing commit
instead of replacing it. Fixed this by checking out the master branch
again before creating the commit.

The jobs in the deploy stage have to be triggered manually in GitLab.
There is one deploy job for each project which uses the gitlab-ci
scripts as a submodule, so that the deployment can be performed step by
step.

If executed within MR context, an integration MR is created and left
open. The user can extend this integration MR, e.g. if CI scripts have
been renamed, changed command line arguments or other changes requiring
updates of the correspronding .gitlab-ci.yml file. Subsequent runs of
this job will re-create the integration branch, so manual changes are
lost in this case.

If executed on the master branch (i.e. after the source MR has been
merged), the job does exactly the same, plus the integration MR will be
automatically merged. If this fails, the job will fail as well.