Parallelize the Travis run using build stages (#886)

Parallelize the travis run using build stages

https://docs.travis-ci.com/user/build-stages/

This will run source checks first (style, lint) and then if all pass,
kick off all platforms and builds in parallel.

1 files changed, 74 insertions, 0 deletions

diff --git a/scripts/if_changed.sh b/scripts/if_changed.sh
new file mode 100755
index 0000000..616eebb
--- /dev/null
+++ b/scripts/if_changed.sh
@@ -0,0 +1,74 @@
+# Copyright 2018 Google
+#
+# 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.
+
+# Within Travis, runs the given command if the current project has changes
+# worth building.
+#
+# Examines the following Travis-supplied environment variables:
+#   - TRAVIS_PULL_REQUEST - the PR number or false for full build
+#   - TRAVIS_COMMIT_RANGE - the range of commits under test; empty on a new
+#     branch
+#
+# Also examines the following configured environment variables that should be
+# specified in an env: block
+#   - PROJECT - Firebase or Firestore
+#   - METHOD - xcodebuild or cmake
+
+function check_changes() {
+  if git diff --name-only "$TRAVIS_COMMIT_RANGE" | grep -Eq "$1"; then
+    run=true
+  fi
+}
+
+run=false
+
+# To force Travis to do a full run, change the "false" to "{PR number}" like
+# if [[ "$TRAVIS_PULL_REQUEST" == "904" ]]; then
+if [[ "$TRAVIS_PULL_REQUEST" == "false" ]]; then
+  # Full builds should run everything
+  run=true
+
+elif [[ -z "$TRAVIS_COMMIT_RANGE" ]]; then
+  # First builds on a branch should also run everything
+  run=true
+
+else
+  case "$PROJECT-$METHOD" in
+    Firebase-*)
+      check_changes '^(Firebase|Example)'
+      ;;
+
+    Firestore-xcodebuild)
+      check_changes '^Firestore/(core|third_party)'
+      ;;
+
+    Firestore-cmake)
+      check_changes '^Firestore'
+      ;;
+
+    *)
+      echo "Unknown project-method combo" 1>&2
+      echo "  PROJECT=$PROJECT" 1>&2
+      echo "  METHOD=$METHOD" 1>&2
+      exit 1
+      ;;
+  esac
+fi
+
+if [[ "$run" == true ]]; then
+  "$@"
+else
+  echo "skipped $*"
+fi
+