Add infrastructure

Add several tools to help with the extension development:

- Add generateManifest.bash to generate the manifest.json file
  dynamically, from a template at templates/manifest.gjson. The
  manifest.gjson file can have lines defining what parts of the manifest
  are added for each target browser.
- Add release.bash to generate the extension ZIP files.
- Add Makefile to serve as a wrapper for the release.bash script.
- Add tagRelease.bash to help tag versions in Git accordingly.

Change-Id: I2395556113649ee0221a61a4a7966492bbdad8e8
diff --git a/release.bash b/release.bash
new file mode 100644
index 0000000..d361848
--- /dev/null
+++ b/release.bash
@@ -0,0 +1,103 @@
+#!/bin/bash
+#
+# Generate release files (ZIP archives of the extension source code).
+
+# Prints help text
+function usage() {
+  cat <<END
+
+  Usage: $progname [--channel CHANNEL --browser BROWSER]
+
+  optional arguments:
+    -h, --help     show this help message and exit
+    -c, --channel  indicates the channel of the release. Can be "beta"
+                   or "stable". Defaults to "stable".
+    -b, --browser  indicates the target browser for the release. As of
+                   now it can only be "chromium", which is also the
+                   default value.
+
+END
+}
+
+# Updates manifest.json field
+function set_manifest_field() {
+  sed -i -E "s/\"$1\": \"[^\"]*\"/\"$1\": \"$2\"/" src/manifest.json
+}
+
+# Get options
+opts=$(getopt -l "help,channel:,browser:" -o "hc:b:" -n "$progname" -- "$@")
+eval set -- "$opts"
+
+channel=stable
+browser=chromium
+
+while true; do
+  case "$1" in
+    -h | --help)
+      usage
+      exit
+      ;;
+    -c | --channel)
+      channel="$2"
+      shift 2
+      ;;
+    -b | --browser)
+      browser="$2"
+      shift 2
+      ;;
+    *) break ;;
+  esac
+done
+
+if [[ $channel != "stable" && $channel != "beta" ]]; then
+  echo "channel parameter value is incorrect." >&2
+  usage
+  exit
+fi
+
+if [[ $browser != "chromium" ]]; then
+  echo "browser parameter value is incorrect." >&2
+  usage
+  exit
+fi
+
+echo "Started building release..."
+
+# First of all, generate the appropriate manifest.json file for the
+# target browser
+dependencies=(${browser})
+
+bash generateManifest.bash "${dependencies[@]}"
+
+# This is the version name which git gives us
+version=$(git describe --always --tags --dirty)
+
+# If the version name contains a hyphen then it isn't a release
+# version. This is also the case if it doesn't start with a "v".
+if [[ $version == *"-"* || $version != "v"* ]]; then
+  # As it isn't a release version, setting version number to 0 so it
+  # cannot be uploaded to the Chrome Web Store
+  set_manifest_field "version" "0"
+  set_manifest_field "version_name" "$version-$channel"
+else
+  # It is a release version, set the version fields accordingly.
+  set_manifest_field "version" "${version:1}"
+  set_manifest_field "version_name" "${version:1}-$channel"
+fi
+
+if [[ $channel == "beta" ]]; then
+  # Change manifest.json to label the release as beta
+  set_manifest_field "name" "__MSG_appBetaName__"
+fi
+
+# Create ZIP file for upload to the Chrome Web Store
+mkdir -p out
+rm -rf out/screen-capture-$version-$browser-$channel.zip
+(cd src &&
+  zip -rq ../out/screen-capture-$version-$browser-$channel.zip * \
+  -x "*/.git*" -x "*/\.DS_Store" -x "*/OWNERS")
+
+# Clean generated manifest.json file
+rm -f src/manifest.json
+
+echo "Done!"