Tagging process streamlined

A tagRelease.bash script is created in order to streamline the tagging
process. Now tag messages contain a link to the changelog between
versions.

Change-Id: I14effc4e7586f5d41e5c1df5561350fbe5dc48b7
diff --git a/tagRelease.bash b/tagRelease.bash
new file mode 100644
index 0000000..bc269ca
--- /dev/null
+++ b/tagRelease.bash
@@ -0,0 +1,52 @@
+#!/bin/bash
+#
+# Tags the current git HEAD as a new version, passed via a flag.
+
+GITILES_REPO_URL="https://gerrit.avm99963.com/plugins/gitiles/infinitegforums"
+
+# Prints help text
+function usage() {
+  cat <<END
+
+  Usage: $progname --version VERSION
+
+  required arguments:
+    -v, --version  the version of the new release (in the form vx)
+                   which wants to be tagged.
+
+  optional arguments:
+    -h, --help     show this help message and exit
+
+END
+}
+
+opts=$(getopt -l "help,version:" -o "hv:" -n "$progname" -- "$@")
+eval set -- "$opts"
+
+prevVersion=$(git describe --abbrev=0)
+nextVersion="null"
+
+while true; do
+  case "$1" in
+    -h | --help)
+      usage
+      exit
+      ;;
+    -v | --version)
+      nextVersion="$2"
+      shift 2
+      ;;
+    *) break ;;
+  esac
+done
+
+if [[ $nextVersion == "null" ]]; then
+  echo "version parameter value is incorrect." >&2
+  usage
+  exit
+fi
+
+commitMessage="Changelog: $GITILES_REPO_URL/+log/refs/tags/$prevVersion..refs/tags/$nextVersion"
+git tag -a $nextVersion -m "$commitMessage"
+
+echo "Tag created. Now run \`git push --tags\` to push the tags to the server."