travis: improve our detection of whether we are on a pull request

Reading the docs sometimes pays off

diff --git a/tools/internal/travis-sonarqube.sh b/tools/internal/travis-sonarqube.sh
index d069347..406f86f 100755 (executable)
--- a/tools/internal/travis-sonarqube.sh
+++ b/tools/internal/travis-sonarqube.sh
@@ -40,7 +40,7 @@ installBuildWrapper
 ctest --output-on-failure --timeout 100
 
 # Only run sonar on master (not on pull requests)
-if [ `git rev-parse --abbrev-ref HEAD` != "master" ] ; then
+if [ "$TRAVIS_PULL_REQUEST" != "false" ] ; then
   exit 0
 fi