Restrict trigger push branch for GitHub Workflow

Feature branches rarely need their own CI runs: the code is already
tested when a pull request is opened against a release branch. If the
push trigger has no branch restriction and pull_request is also
configured, every push to a branch with an open PR runs the workflow
twice: once for the push and once for the PR synchronisation.

Always give the push trigger an explicit list of branches: this stops
branches created from a release branch from inheriting its workflow
runs.

see https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=430408443#GitHubActionsRecommendedPractices-Restrictthepushtriggertospecificbranches

Signed-off-by: Aurélien Pupier <apupier@ibm.com>

Author: apupier

.github/workflows/maven.yml

@@ -19,6 +19,8 @@ name: GitHub CI
 
 on:
   push:
+    branches:
+      - master
 #    branches-ignore:
 #      - dependabot/**
   pull_request: