If we push a branch and a tag pointing to the HEAD of this branch, then Travis CI would run the build twice. This wastes resources and slows the testing. Add a function to detect this situation and skip the build the branch if appropriate. Invoke this function on every build. Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Lars Schneider <larsxschneider@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>