feat: release script accepts new_version arg (#264)

* feat: release script accepts new_version arg

This PR teaches the release.sh script how to deal with version numbers
that don't start with a leading 0. This is important since Spanner is
now 1.0.0. release.sh now accepts an optional "new_version" argument to
let the user specify the desired new version number on the command line
rather than computing it from previous tags. This is useful when we want
to jump to a non-sequential version number. For example, this would have
worked for the Spanner 1.0.0 release we did a few days ago.

* PR comments + some refactoring

* pr comments

Author: devjgm

release/release.sh

@@ -1,21 +1,25 @@
 #!/bin/bash
 #
 # Usage:
-#   $ release.sh [-f] <organization/project-name>
+#   $ release.sh [-f] <organization/project-name> [<new-version>]
+#
+#   Args:
+#     organization/project-name    Required. The GitHub repo to release.
+#
+#     new-version                  Optional. The new version number to use,
+#                                  specified as M.N.0. If not specified, the
+#                                  new version will be computed from existing
+#                                  git tags. This flag should only be needed
+#                                  when jumping to a non-sequential version
+#                                  number.
 #
 #   Options:
 #     -f     Force; actually make and push the changes
 #     -h     Print help message
 #
-# Example:
-#   # Shows what commands would be run. NO CHANGES ARE PUSHED
-#   $ release.sh googleapis/google-cloud-cpp-spanner
-#
-#   # Shows commands AND PUSHES changes when -f is specified
-#   $ release.sh -f googleapis/google-cloud-cpp-spanner
-#
 # This script creates a "release" on github by doing the following:
-#   1. Computes the next version to use
+#
+#   1. Computes the next version to use, if not specified on the command line
 #   2. Creates and pushes the tag w/ the new version
 #   3. Creates and pushes a new branch w/ the new version
 #   4. Creates the "Pre-Release" in the GitHub UI.
@@ -25,37 +29,65 @@
 # happen. Then run this script. After running this script, the user must still
 # go to the GH UI where the new release will exist as a "pre-release", and edit
 # the release notes.
+#
+# Examples:
+#
+#   # NO CHANGES ARE PUSHED. Shows what commands would be run.
+#   $ release.sh googleapis/google-cloud-cpp-spanner
+#
+#   # NO CHANGES ARE PUSHED. Shows what commands would be run.
+#   $ release.sh googleapis/google-cloud-cpp-spanner 2.0.0
+#
+#   # PUSHES CHANGES to release -spanner
+#   $ release.sh -f googleapis/google-cloud-cpp-spanner
+#
+#   # PUSHES CHANGES to release -spanner, setting its new version to 2.0.0
+#   $ release.sh -f googleapis/google-cloud-cpp-spanner 2.0.0
 
 set -eu
 
 # Extracts all the documentation at the top of this file as the usage text.
 readonly USAGE="$(sed -n '3,/^$/s/^# \?//p' "$0")"
 
+# Takes an optional list of strings to be printed with a trailing newline and
+# exits the program with code 1
+function die_with_message() {
+  for m in "$@"; do
+    echo "$m" 1>&2
+  done
+  exit 1
+}
+
 FORCE_FLAG="no"
 while getopts "fh" opt "$@"; do
   case "$opt" in
     [f])
       FORCE_FLAG="yes";;
     [h])
-      echo "$USAGE"
+      echo "${USAGE}"
       exit 0;;
     *)
-      echo "$USAGE"
-      exit 1;;
+      die_with_message "${USAGE}";;
   esac
 done
 shift $((OPTIND - 1))
 declare -r FORCE_FLAG
 
-if [[ $# -ne 1 ]]; then
-  echo "Missing repo name, example googleapis/google-cloud-cpp-spanner"
-  echo "$USAGE"
-  exit 1;
+PROJECT_ARG=""
+VERSION_ARG=""
+if [[ $# -eq 1 ]]; then
+  PROJECT_ARG="$1"
+elif [[ $# -eq 2 ]]; then
+  PROJECT_ARG="$1"
+  VERSION_ARG="$2"
+else
+  die_with_message "Invalid arguments" "${USAGE}"
 fi
+declare -r PROJECT_ARG
+declare -r VERSION_ARG
 
-readonly PROJECT="$1"
-readonly CLONE_URL="[email protected]:${PROJECT}.git"
-readonly TMP_DIR="$(mktemp -d "/tmp/${PROJECT//\//-}-release.XXXXXXXX")"
+readonly CLONE_URL="[email protected]:${PROJECT_ARG}.git"
+readonly TMP_DIR="$(mktemp -d "/tmp/${PROJECT_ARG//\//-}-release.XXXXXXXX")"
 readonly REPO_DIR="${TMP_DIR}/repo"
 
 function banner() {
@@ -87,25 +119,40 @@ trap exit_handler EXIT
 # of the release. We also use 'hub' to do the clone so that the user is asked
 # to authenticate at the beginning of the process rather than at the end.
 if ! command -v hub > /dev/null; then
-  echo "Can't find 'hub' command"
-  echo "Maybe run: sudo apt install hub"
-  echo "Or build it from https://github.com/github/hub"
-  exit 1
+  die_with_message \
+    "Can't find 'hub' command" \
+    "Maybe run: sudo apt install hub" \
+    "Or build it from https://github.com/github/hub"
 fi
 
-banner "Starting release for ${PROJECT} (${CLONE_URL})"
-hub clone "${PROJECT}" "${REPO_DIR}"  # May force login to GH at this point
+banner "Starting release for ${PROJECT_ARG} (${CLONE_URL})"
+hub clone "${PROJECT_ARG}" "${REPO_DIR}"  # May force login to GH at this point
 cd "${REPO_DIR}"
 
 # Figures out the most recent tagged version, and computes the next version.
 readonly TAG="$(git describe --tags --abbrev=0 origin/master)"
 readonly CUR_TAG="$(test -n "${TAG}" && echo "${TAG}" || echo "v0.0.0")"
-readonly NEW_RELEASE="$(perl -pe 's/v0.(\d+).0/"v0.${\($1+1)}"/e' <<<"${CUR_TAG}")"
-readonly NEW_TAG="${NEW_RELEASE}.0"
-readonly NEW_BRANCH="${NEW_RELEASE}.x"
+readonly CUR_VERSION="${CUR_TAG#v}"
+
+NEW_VERSION=""
+if [[ -n "${VERSION_ARG}" ]]; then
+  NEW_VERSION="${VERSION_ARG}"
+else
+  # No new version specified; compute the new version number
+  NEW_VERSION="$(perl -pe 's/(\d+).(\d+).(\d+)/"$1.${\($2+1)}.$3"/e' <<<"${CUR_VERSION}")"
+fi
+declare -r NEW_VERSION
+
+# Avoid handling patch releases for now, because we wouldn't need a new branch
+# for those.
+if ! grep -P "\d+\.\d+\.0" <<<"${NEW_VERSION}" > /dev/null; then
+  die_with_message "Sorry, cannot handle patch releases (yet)" "${USAGE}"
+fi
+
+readonly NEW_TAG="v${NEW_VERSION}"
+readonly NEW_BRANCH="${NEW_TAG%.0}.x"
 
-banner "Release info for ${NEW_RELEASE}"
-echo "Current tag: ${CUR_TAG}"
+banner "Release info for ${CUR_TAG} -> ${NEW_TAG}"
 echo "    New tag: ${NEW_TAG}"
 echo " New branch: ${NEW_BRANCH}"