Here again for more Jenkins jobs tuning.

I noticed that when submitting a Phabricator Diff, Jenkins will create a build
job for each branch that has been modified since the last build.

For instance, I have tagged swh-web to a new version (0.0.207). Once pushed
to the remote repository, debian packages are built and some new commits are
issued and pushed into the debian/* and origin/pristine-tar branches.

After that I have submitted D1837 that triggered three jobs in each Phabricator
Diff related projects (#655, #656, #657 for the Python Diff project and
#251, #252, #253 for the cypress Diff project.

As you can see there is two useless extra jobs executed in each project in that case.

So configure Jenkins Git plugin to only fetch the master branch to avoid that annoying behavior.