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+#!/bin/bash
+#
+# Copyright 2017 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+#
+# Generate git strings for tagging EC branches.
+#
+# This script builds up on ideas put by vpalatin@ into util/getversion.sh
+#
+# Git allows to count number of patches between the current state of the tree
+# and any directly preceding tag in the tree. That is if we tag the first
+# patch in the current branch, we can tell how many patches are in the branch
+# above that tag. And if we tag the branch such that the tag string includes
+# the branch name, we can also say what branch we are in looking at the
+# closest tag in the tree.
+#
+# This admittedly brittle script automates the process of tagging for the EC
+# git tree in Chrome OS repo, but it could be used for any other Chrome OS
+# repo git tree just as well.
+#
+# The script is brittle because it relies on the following assumptions which
+# are true for Chrome OS repo at the time of writing:
+#
+# - the upstream branch alias name shows up in the 'git branch -a' output
+#   separated by ->
+# - the upstream branch alias name has the format of
+#   cros/<branch name>
+# - the remote git server name shows up in 'git config -l' output in the
+#   line starting with "remote.cros.url="
+# - firmware branch names have format of firmware-<board>-XXXXXX
+# - the current branch was cut off of <remote name>/master
+#
+# The tag name generated by this script would be the XXXXX string with dots,
+# if any, replaced by underscores.
+
+# Retrieve the upstream branch alias name
+UPSTREAM="$(git branch -a | awk '/->/ {print $3}')"
+if [[ -z "${UPSTREAM}" ]]; then
+  echo "Failed to determine upstream branch alias" >&2
+  exit 1
+fi
+
+export ORIGIN_NAME="cros"
+ORIGIN="$(git config "remote.${ORIGIN_NAME}.url")"
+
+# The last common patch between this branch and the master.
+BRANCH_POINT="$(git merge-base "${UPSTREAM}" "${ORIGIN_NAME}/master")"
+if [[ -z "${BRANCH_POINT}" ]]; then
+  echo "Failed to determine cros/master branch point" >&2
+  exit 1
+fi
+
+# Derive tag base string from the upstream branch name as described above.
+TAG_BASE="$(sed 's/.*-//       # drop everything up to including the last -
+                 s/\./_/g      # replace dots and dashes with underscores
+      ' <<< "${UPSTREAM}" )"
+
+if [[ "${TAG_BASE}" == "master" ]]; then
+  echo "Nothing to tag in master branch" >&2
+  exit 1
+fi
+
+TAG="v1.${TAG_BASE}.0"
+
+#SHA1 of the first patch of this branch
+BASE_SHA="$(git rev-list --ancestry-path "${BRANCH_POINT}".."${UPSTREAM}" |
+    tail -1)"
+
+if git tag -a -m 'firmware branch ${TAG}' "${TAG}" "${BASE_SHA}"; then
+  cat <<EOF
+
+A new tag '$TAG' has been set. Use the following command
+to push it to the server
+
+git push --tags ${ORIGIN} ${TAG}
+
+Or if you want to delete it:
+
+git tag -d $TAG
+
+EOF
+fi