Make Travis only build/run affected targets. (#32)

Many Travis builds that require compiling protos are taking a very long time; this will hopefully help somewhat.

Author: isturdy

.travis.yml

@@ -10,7 +10,4 @@ before_install:
   - ./bazel-0.8.1-installer-linux-x86_64.sh --user
 
 script:
-  # We can't use --noshow_progress because Travis terminates the
-  # build after 10 mins without output.
-  - bazel build --experimental_ui_actions_shown=1 -k $(bazel query ... | grep -v :_)
-  - bazel test --experimental_ui_actions_shown=1 -k $(bazel query "kind(test, //...) except attr('tags', 'noci', //...)" | grep -v :_)
+  - ./ci.sh

ci.sh

@@ -0,0 +1,58 @@
+#! /usr/bin/env bash
+#
+# Copyright 2018, 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.
+
+# Build/run only targets affected by files changed in the commit range,
+# according to bazel query. Based on
+# https://github.com/bazelbuild/bazel/blob/master/scripts/ci/ci.sh
+
+files=()
+# If WORKSPACE or .travis.yml is touched, almost anything may be affected.
+# Otherwise, top-level files are irrelevant to the build and we exclude them to
+# suppress query errors.
+if [[ ! -z $(git diff --name-only ${TRAVIS_COMMIT_RANGE} \
+  | grep "WORKSPACE\|.travis.yml" ) ]];
+then
+  echo ".travis.yml or WORKSPACE affected; running all tests."
+  files=("//...")
+else
+  echo "Affected files:"
+  for file in $(git diff --name-only ${TRAVIS_COMMIT_RANGE} | grep / ); do
+    mapfile -O ${#files[@]} -t files <<< "$(bazel query $file)"
+    bazel query $file
+  done
+fi
+
+# We can't use --noshow_progress on build/test commands because Travis
+# terminates the build after 10 mins without output.
+buildables=$(bazel query -k --noshow_progress \
+  "kind(rule, rdeps(//..., set(${files[*]})))" \
+  | grep -v :_)
+if [[ ! -z $buildables ]]; then
+  echo "Building targets"
+  echo "$buildables"
+  bazel build --experimental_ui_actions_shown=1 -k $buildables
+fi
+
+# Exclude tests tagged "noci". Tests marked "manual" are already excluded from
+# wildcard queries.
+tests=$(bazel query -k --noshow_progress \
+  "kind(test, rdeps(//..., set(${files[*]}))) except attr('tags', 'noci', //...)" \
+  | grep -v :_)
+if [[ ! -z $tests ]]; then
+  echo "Running tests"
+  echo "$tests"
+  bazel test --experimental_ui_actions_shown=1 -k $tests
+fi