Evaluate PR state & set branch to commit accordingly

tests/ci_git_prep.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+THIS_BRANCH=0
+
+git_setup() {
+  git config --global user.email "travis@travis-ci.org"
+  git config --global user.name "Travis CI"
+}
+
+set_branch() {
+  if [ "$TRAVIS_PULL_REQUEST" = "true" ]; then
+    THIS_BRANCH=$TRAVIS_PULL_REQUEST_BRANCH
+  else
+    THIS_BRANCH='master'
+  fi
+}
+
+git_setup
+git fetch
+set_branch
+git checkout $THIS_BRANCH
+exit 0