add travis branch

Author: 3nids

.docker/docker-compose.travis.yml

@@ -14,6 +14,7 @@ services:
     environment:
       - CCACHE_DIR=/root/.ccache
       - TRAVIS_BUILD_DIR=${TRAVIS_BUILD_DIR}
+      - TRAVIS_BRANCH=${TRAVIS_BRANCH}
       - TRAVIS_PULL_REQUEST=${TRAVIS_PULL_REQUEST}
       - TRAVIS_PULL_REQUEST_BRANCH=${TRAVIS_PULL_REQUEST_BRANCH}
       - TRAVIS_COMMIT_RANGE=${TRAVIS_COMMIT_RANGE}