diff --git a/tests/update_reference_data.sh b/tests/update_reference_data.sh
index 4430677c73..c0fd645686 100755
--- a/tests/update_reference_data.sh
+++ b/tests/update_reference_data.sh
@@ -1,55 +1,155 @@
-#!/bin/bash
+#!/bin/bash -norc
+
+# Generate OPM-Tests repository PR to update one or more reference
+# solution files as a result of a known improvement to the simulator
+# or a new regression test being added into the test suite.
+#
+# Processes 'LastTestsFailed.log' in OPM-Simulators' build directory
+# to infer applicable failing tests.
+#
+# Positional arguments:
+#   - $1 Location of OPM-Tests root directory.
+#   - $2 Location of OPM-Simulators' build directory.
+#   - $3 Full path to 'convertECL' utility, including the 'convertECL'
+#        utility name. Needed only if caller wants 'diff -u' style
+#        content differences between existing reference solutions and
+#        new candidate solutions. Pass empty string if not.
+#
+# Environment:
+#   - $WORKSPACE Location of Jenkins' build work space.
+#   - $configuration Name of Jenkins build configuration.
+#   - $REASON Underlying reason for this data update. Typically one or
+#     more PR names. An empty REASON will stop commit process and
+#     prompt user for an appropriate commit message.
+#   - $BRANCH_BASE Branch relative to which to start this data
+#     update. Typically 'master'.
+#   - $BRANCH_NAME Name of data update PR branch in OPM-Tests repo.
 
 OPM_TESTS_ROOT=$1
 BUILD_DIR=$2
 CONVERT_ECL=$3
 
-TMPDIR=`mktemp -d`
-mkdir $TMPDIR/orig
-mkdir $TMPDIR/new
+TMPDIR=$(mktemp -d)
+mkdir -p "${TMPDIR}"/{orig,new}
 
-# Copy results from a test run to refence dir
+# Location of this script.
+dir=$(dirname $0)
+
+# Tests that are ultimately updated in this script run. Aggregated
+# mostly in order to create the final commit message.
+changed_tests=""
+
+# Collection of properties for the test currently being processed.
+# Populated by function extractTestProperties().
+declare -A testProperty
+
+# ===========================================================================
+# Helper functions.
+
+# Generate textual diffs of formatted file contents.
+#
+# Appends to ${WORKSPACE}/data_diff.
+#
+# $1 is location of reference results
+# $2 is location of new simulation results
+# $3 is name of result file.
+compareResultFileContents () {
+    local reference_dir="${1}"
+    local simoutput_dir="${2}"
+    local result_file="${3}"
+
+    # Recall: convertECL prints a line of the form
+    #
+    #    converting path/to/CASE.UNRST -> path/to/CASE.FUNRST
+    #
+    # so we use this output to infer the result file name.
+
+    cp -a "${reference_dir}/${result_file}" "${TMPDIR}/orig"
+    ref=$(${CONVERT_ECL} "${TMPDIR}/orig/${result_file}" | awk '/converting/{print $NF}')
+
+    cp -a "${simoutput_dir}/${result_file}" "${TMPDIR}/new"
+    new=$(${CONVERT_ECL} "${TMPDIR}/new/${result_file}" | awk '/converting/{print $NF}')
+
+    diff -u "${ref}" "${new}" >> "${WORKSPACE}/data_diff"
+}
+
+# Extract individual test properties of a failed test
+#
+# Input argument $1 is the test description from 'LastTestsFailed.log'.
+#
+# Populates 'testProperty' in such a way that
+#
+#   ${testProperty["binary"]}    is the simulation tool used to run the test.
+#   ${testProperty["dir_name"]}  is the source directory in opm-tests.
+#   ${testProperty["file_name"]} is the base name of the simulation input file.
+#   ${testProperty["test_name"]} is the test suite's name of the particular test.
+extractTestProperties () {
+    local failed_test
+
+    failed_test=$(echo "$1" | sed -e 's/.*://' -e 's/\+/./g')
+
+    testProperty["binary"]=$(awk -v search="set_tests_properties\\\(${failed_test}\$" \
+                             -v prop="SIMULATOR" -f "${dir}/getprop.awk" \
+                             "${BUILD_DIR}/CTestTestfile.cmake")
+
+    testProperty["dir_name"]=$(awk -v search="set_tests_properties\\\(${failed_test}\$" \
+                               -v prop="DIRNAME" -f "${dir}/getprop.awk" \
+                               "${BUILD_DIR}/CTestTestfile.cmake")
+
+    testProperty["file_name"]=$(awk -v search="set_tests_properties\\\(${failed_test}\$" \
+                                -v prop="FILENAME" -f "${dir}/getprop.awk" \
+                                "${BUILD_DIR}/CTestTestfile.cmake")
+
+    testProperty["test_name"]=$(awk -v search="set_tests_properties\\\(${failed_test}\$" \
+                                -v prop="TESTNAME" -f "${dir}/getprop.awk" \
+                                "${BUILD_DIR}/CTestTestfile.cmake")
+}
+
+# Copy results from a test run to reference dir
+#
 # $1 = source directory to copy data from
 # $2 = destination directory to copy data to
 # $3 = base file name for files to copy
 # $4...$@ = file types to copy
 copyToReferenceDir () {
-  SRC_DIR=$1
-  DST_DIR=$2
-  STEM=$3
-  FILETYPES=${@:4}
-  mkdir -p $DST_DIR
+    SRC_DIR=$1
+    DST_DIR=$2
+    STEM=$3
+    FILETYPES=${@:4}
+    mkdir -p "${DST_DIR}"
 
-  DIFF=1
-  for filetype in $FILETYPES
-  do
-    # Don't flag as changed if both reference and result dir lack a file type
-    # In particular to handle the optional RFT's
-    if [ ! -f $SRC_DIR/$STEM.$filetype ] && [ ! -f $DST_DIR/$STEM.$filetype ]
-    then
-      continue
-    fi
-    diff -q "$SRC_DIR/$STEM.$filetype" "$DST_DIR/$STEM.$filetype"
-    res=$?
-    if test $res -ne 0 && test -n "$CONVERT_ECL"
-    then
-      cp $SRC_DIR/$STEM.$filetype $TMPDIR/new
-      $CONVERT_ECL $TMPDIR/new/$STEM.$filetype
-      cp $DST_DIR/$STEM.$filetype $TMPDIR/orig
-      $CONVERT_ECL $TMPDIR/orig/$STEM.$filetype
-      diff -u $TMPDIR/orig/$STEM.F$filetype $TMPDIR/new/$STEM.F$filetype >> $WORKSPACE/data_diff
-    fi
-    if test $res -ne 0
-    then
-      cp "$SRC_DIR/$STEM.$filetype" $DST_DIR
-      DIFF=0
-    fi
-  done
+    DIFF=1
+    for filetype in $FILETYPES
+    do
+        result_file="${STEM}.${filetype}"
 
-  return $DIFF
+        # Don't flag results as changed if neither the reference nor
+        # the result directory have a specific file type. This means
+        # we transparently handle result files like *.RFT which are
+        # created only if the simulation model explicitly requests the
+        # file type.
+        if [ ! -f "${SRC_DIR}/${result_file}" -a ! -f "${DST_DIR}/${result_file}" ]
+        then
+            continue
+        fi
+
+        if ! cmp -s "${SRC_DIR}/${result_file}" "${DST_DIR}/${result_file}"
+        then
+            if  [ -n "$CONVERT_ECL" ]
+            then
+                compareResultFileContents "${DST_DIR}" "${SRC_DIR}" "${result_file}"
+            fi
+
+            cp -a "${SRC_DIR}/${result_file}" "${DST_DIR}"
+            DIFF=0
+        fi
+    done
+
+    return $DIFF
 }
 
-# Copy damaris results from a test run to refence dir
+# Copy damaris results from a test run to reference dir
+#
 # $1 = source directory to copy data from
 # $2 = destination directory to copy data to
 # $3 = base file name for files to copy
@@ -69,68 +169,156 @@ copyDamarisToReferenceDir () {
   done
 }
 
-changed_tests=""
+# Generate reference solution updates for restarted simulation runs.
+#
+# $1 is name of simulator binary
+# $2 is location of reference solutions in opm-tests
+# $3 is base name of simulation input file
+# $4 is test suite's name of test base run
+updateRestartResults () {
+    local binary="${1}"
+    local dir_name="${2}"
+    local file_name="${3}"
+    local test_name="${4}"
 
-# Read failed tests
-FAILED_TESTS=`cat $BUILD_DIR/Testing/Temporary/LastTestsFailed*.log`
+    local rst_steps
+    local rst_step
+    local result
+    local case_result
 
-test -z "$FAILED_TESTS" && exit 5
+    rst_steps=$(echo ${BUILD_DIR}/tests/results/${binary}+${test_name}/restart/*RESTART_*.UNRST | \
+                    sed -E -e 's;[^ ]*RESTART_([0-9]+)\.UNRST;\1;g')
 
-for failed_test in $FAILED_TESTS
-do
-  grep -q -E "compareECLFiles|compareDamarisFiles" <<< $failed_test
-  test $? -ne 0 && continue
-  failed_test=`echo $failed_test | sed -e 's/.*://g' -e 's/\+/./g'`
-  # Extract test properties
-  dir=`dirname "$0"`
-  binary=$(awk -v search="set_tests_properties\\\($failed_test\$" -v prop="SIMULATOR" -f $dir/getprop.awk $BUILD_DIR/CTestTestfile.cmake)
-  dir_name=$(awk -v search="set_tests_properties\\\($failed_test\$" -v prop="DIRNAME" -f $dir/getprop.awk $BUILD_DIR/CTestTestfile.cmake)
-  file_name=$(awk -v search="set_tests_properties\\\($failed_test\$" -v prop="FILENAME" -f $dir/getprop.awk $BUILD_DIR/CTestTestfile.cmake)
-  test_name=$(awk -v search="set_tests_properties\\\($failed_test\$" -v prop="TESTNAME" -f $dir/getprop.awk $BUILD_DIR/CTestTestfile.cmake)
-  echo "$failed_test ${binary} ${dirname} ${file_name} ${test_name}"
-  if grep -q compareECLFiles <<< $failed_test
-  then
-    copyToReferenceDir \
-            $BUILD_DIR/tests/results/$binary+$test_name \
-            $OPM_TESTS_ROOT/$dir_name/opm-simulation-reference/$binary \
-            $file_name \
-            EGRID INIT RFT SMSPEC UNRST UNSMRY
-    test $? -eq 0 && changed_tests="$changed_tests $test_name"
-
-    if [ -d $configuration/build-opm-simulators/tests/results/$binary+$test_name/restart ]
-    then
-
-      RSTEPS=`ls -1 $BUILD_DIR/tests/results/$binary+$test_name/restart/*.UNRST | sed -e 's/.*RESTART_*//' | sed 's/[.].*//' `
-      result=0
-      for RSTEP in $RSTEPS
-      do
+    result=0
+    for rst_step in ${rst_steps}
+    do
         copyToReferenceDir \
-            $BUILD_DIR/tests/results/$binary+$test_name/restart/ \
-            $OPM_TESTS_ROOT/$dir_name/opm-simulation-reference/$binary/restart \
-            ${file_name}_RESTART_${RSTEP} \
+            "${BUILD_DIR}/tests/results/${binary}+${test_name}/restart/" \
+            "${OPM_TESTS_ROOT}/${dir_name}/opm-simulation-reference/${binary}/restart" \
+            "${file_name}_RESTART_${rst_step}" \
             EGRID INIT RFT SMSPEC UNRST UNSMRY
-        res=$?
-        test $result -eq 0 || result=$res
-      done
-      test $result -eq 0 && changed_tests="$changed_tests $test_name(restart)"
+
+        case_result=$?
+        if [ ${result} -eq 0 ]
+        then
+            result=${case_result}
+        fi
+    done
+
+    if [ ${result} -eq 0 ]
+    then
+        changed_tests+=" ${test_name}(restart)"
     fi
-  else
+}
+
+# Generate reference solution updates for base and restarted
+# simulation runs.
+#
+# Uses properties of failing test being processed (${testProperty}).
+updateFullSimulationResults () {
+    local binary=${testProperty["binary"]}
+    local dir_name=${testProperty["dir_name"]}
+    local file_name=${testProperty["file_name"]}
+    local test_name=${testProperty["test_name"]}
+
+    if copyToReferenceDir \
+           "${BUILD_DIR}/tests/results/${binary}+${test_name}" \
+           "${OPM_TESTS_ROOT}/${dir_name}/opm-simulation-reference/${binary}" \
+           "${file_name}" \
+           EGRID INIT RFT SMSPEC UNRST UNSMRY
+    then
+        changed_tests+=" ${test_name}"
+    fi
+
+    if [ -d "${configuration}/build-opm-simulators/tests/results/${binary}+${test_name}/restart" ]
+    then
+        updateRestartResults "${binary}" "${dir_name}" "${file_name}" "${test_name}"
+    fi
+}
+
+# Generate reference solution updates for Damaris result files.
+#
+# Uses properties of failing test being processed (${testProperty}).
+updateDamarisResults () {
+    local binary=${testProperty["binary"]}
+    local dir_name=${testProperty["dir_name"]}
+    local file_name=${testProperty["file_name"]}
+    local test_name=${testProperty["test_name"]}
+
     copyDamarisToReferenceDir \
-            $BUILD_DIR/tests/results/$binary+$test_name \
-            $OPM_TESTS_ROOT/$dir_name/opm-simulation-reference/$binary \
-            $file_name
-    changed_tests="$changed_tests $test_name"
-  fi
+        "${BUILD_DIR}/tests/results/${binary}+${test_name}" \
+        "${OPM_TESTS_ROOT}/${dir_name}/opm-simulation-reference/${binary}" \
+        "${file_name}"
+
+    changed_tests+=" ${test_name}"
+}
+
+# Update .INIT and .EGRID files for Norne model as applicable.
+#
+# This is a special case.
+updateNorneInitFiles () {
+    if copyToReferenceDir \
+        "${BUILD_DIR}/tests/results/init/flow+norne" \
+        "${OPM_TESTS_ROOT}/norne/opm-simulation-reference/flow" \
+        NORNE_ATW2013 \
+        EGRID INIT
+    then
+        changed_tests+=" norne_init"
+    fi
+}
+
+# ===========================================================================
+# Main data update loop.
+#
+# Processes one line of 'LastTestsFailed.log' at a time and updates
+# applicable reference solutions.
+
+for logfile in $(echo "${BUILD_DIR}/Testing/Temporary/LastTestsFailed*.log")
+do
+    if [ ! -s "${logfile}" ]
+    then
+        continue
+    fi
+
+    while read failed_test
+    do
+        if ! grep -q 'compare.*Files_.*' <<< ${failed_test}
+        then
+            # The ${failed_test} is not among the compare*Files_* tests to
+            # which this update script applies.  Nothing to do.
+            continue
+        fi
+
+        # If we get here, the ${failed_test} is one of the compare*Files_*
+        # tests.  Extract specific information about the test itself and
+        # update its reference solutions accordingly.
+
+        extractTestProperties "${failed_test}"
+
+        case "${failed_test}" in
+            *compareECLFiles* )
+                updateFullSimulationResults ;;
+
+            *compareDamarisFiles* )
+                updateDamarisResults ;;
+        esac
+    done < "${logfile}"
 done
 
-# special tests
-copyToReferenceDir \
-      $BUILD_DIR/tests/results/init/flow+norne \
-      $OPM_TESTS_ROOT/norne/opm-simulation-reference/flow \
-      NORNE_ATW2013 \
-      EGRID INIT
-test $? -eq 0 && changed_tests="$changed_tests norne_init"
+# Special case handling of certain particular tests.
+updateNorneInitFiles
 
+if [ -z "${changed_tests}" ]
+then
+    exit 5
+fi
+
+# ===========================================================================
+# Create data update PR.
+
+# 1) Create commit message (or commit message template, depending on
+# the contents of ${REASON}).  Empty ${REASON} ultimately starts an
+# interactive commit.
 changed_tests=`echo $changed_tests | xargs`
 echo -e "Automatic Reference Data Update for ${REASON:-(Unknown)}\n" > /tmp/cmsg
 if [ -z "$REASON" ]
@@ -153,24 +341,29 @@ then
 fi
 
 echo -e "\n### Changed Tests ###\n" >> /tmp/cmsg
-for t in ${changed_tests}
-do
-  echo "  * ${t}" >> /tmp/cmsg
-done
+printf "  * %s\n" ${changed_tests} >> /tmp/cmsg
 
+# ---------------------------------------------------------------------------
+
+# 2) Create branch for new commit.
 cd $OPM_TESTS_ROOT
 if [ -n "$BRANCH_NAME" ]
 then
   git checkout -b $BRANCH_NAME $BRANCH_BASE
 fi
 
-# Add potential new files
+# ---------------------------------------------------------------------------
+
+# 3) Add new files as needed.
 untracked=`git status --porcelain | awk '$1~/\?/{print $2}'`
 if [ -n "$untracked" ]
 then
   git add $untracked
 fi
 
+# ---------------------------------------------------------------------------
+
+# 4) Commit reference solution update.
 if [ -z "$REASON" ]
 then
   git commit -a -t /tmp/cmsg
@@ -178,4 +371,7 @@ else
   git commit -a -F /tmp/cmsg
 fi
 
+# ===========================================================================
+# Clean up intermediate files.
+
 rm -rf $TMPDIR