Add travis check for filename spaces

scripts/check.sh

@@ -212,6 +212,7 @@ fi
 
 # Check lint errors.
 "${top_dir}/scripts/check_whitespace.sh"
+"${top_dir}/scripts/check_filename_spaces.sh"
 "${top_dir}/scripts/check_copyright.sh"
 "${top_dir}/scripts/check_no_module_imports.sh"
 "${top_dir}/scripts/check_test_inclusion.py"

scripts/check_filename_spaces.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+
+# Copyright 2019 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.
+
+# Fail on spaces in file names, excluding the patterns listed below.
+
+# A sed program that removes filename patterns that are allowed to have spaces
+# in them.
+function remove_valid_names() {
+  sed '
+    # Xcode-generated asset files
+    /Assets.xcassets/ d
+
+    # Files without spaces
+    /^[^ ]*$/ d
+  '
+}
+
+count=$(git ls-files | remove_valid_names | wc -l | xargs)
+
+if [[ ${count} != 0 ]]; then
+  echo 'ERROR: Spaces in filenames are not permitted in this repo. Please fix.'
+  echo ''
+
+  git ls-files | remove_valid_names
+  exit 1
+fi