Add helper script for generating a coverage report. (#332)

Author: g-easy

tools/coverage.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+# Copyright 2019, OpenCensus Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# Builds a coverage report.
+
+if [[ ! -e tools/coverage.sh ]]; then
+  echo "This tool must be run from the topmost OpenCensus directory." >&2
+  exit 1
+fi
+
+if ! which genhtml >/dev/null; then
+  echo "Install lcov to get the genhtml program."
+  exit 1
+fi
+
+set -e
+OUTDIR=/tmp/opencensus-coverage
+
+bazel coverage ...
+genhtml --show-details --legend --output-directory $OUTDIR \
+  $(find bazel-out/ -name coverage.dat)
+ls -l $OUTDIR/index.html