Add script to generate a scene diff for a failed regression test (#384)

tests/update_scene_from_travis.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+
+if [ -z "$1" ]
+  then
+    echo "Error: TravisCI job id is required."
+fi
+
+# These variable names should match the ones in .travis.yml
+PATCH_BEGIN_LINE='cat tests_scenes_diff.patch'
+PATCH_END_LINE='echo "scene diff path ends"'
+
+JOB_ID=$1
+RAW_LOG_URL=https://api.travis-ci.org/v3/job/${JOB_ID}/log.txt
+
+REPO_ROOT=$(dirname $0)/..
+
+cd $REPO_ROOT
+
+PWD=$(pwd)
+LOCAL_LOG_FILE=travis_${JOB_ID}_log.txt
+GIT_PATCH_FILE=${JOB_ID}_scene_diff.patch
+
+echo "Download travis build log from $RAW_LOG_URL"
+echo "Store to $PWD/$LOCAL_LOG_FILE"
+curl ${RAW_LOG_URL} --output $LOCAL_LOG_FILE
+
+BEGIN_LINE_NUMBER=$(awk "/${PATCH_BEGIN_LINE}/{ print NR; exit }" $LOCAL_LOG_FILE)
+END_LINE_NUMBER=$(awk "/${PATCH_END_LINE}/{ print NR; exit }" $LOCAL_LOG_FILE)
+sed -n "$((${BEGIN_LINE_NUMBER} + 1)),$((${END_LINE_NUMBER} - 1))p" $LOCAL_LOG_FILE > $GIT_PATCH_FILE
+
+git apply --verbose --ignore-whitespace --reject $GIT_PATCH_FILE 
+
+rm $LOCAL_LOG_FILE
+rm $GIT_PATCH_FILE
+
+cd -