upstream-mattermost/server/scripts/get_latest_release.sh

#!/usr/bin/env bash
# $1 - repo to check against
# $2 - release branch pattern to match
# This script will check if the current repo has version pattern $2 ('release-5.20') in the branch name.
# If it does it will check for a matching release version in the $1 repo and if found check for the newest dot version.
# If the branch pattern isn't found than it will default to the newest release available in $1.
REPO_TO_USE=$1
BRANCH_TO_USE=$2

BASIC_AUTH=""

# If we find a github username and token, we use that.
# In CI, these variables are available and useful to avoid rate limits which is
# much more strict for unauthenticated requests.
if [[ ! -z "$GITHUB_USERNAME" && ! -z "$GITHUB_TOKEN" ]];
then
  BASIC_AUTH="--user $GITHUB_USERNAME:$GITHUB_TOKEN"
fi

LATEST_RELEASE=$(curl \
  --silent \
  $BASIC_AUTH \
  "https://api.github.com/repos/$REPO_TO_USE/releases/latest")

RELEASES=$(curl \
  --silent \
  $BASIC_AUTH \
  "https://api.github.com/repos/$REPO_TO_USE/releases")

LATEST_REL=$(echo "$LATEST_RELEASE" | grep '"tag_name":' | sed -E 's/.*"([^"]+)".*/\1/')

DRAFT=$(echo "$LATEST_RELEASE" | grep '"draft":' | sed -E 's/.*: ([^,]+).*/\1/')

PRERELEASE=$(echo "$RELEASES" | grep '"prerelease":' | sed -E 's/.*: ([^,]+).*/\1/')

# Check if this is a release branch
THIS_BRANCH=$(git rev-parse --abbrev-ref HEAD)
#THIS_BRANCH="release-5.27"# - Used to test release logic on a non release branch

if [[ "$THIS_BRANCH" =~ $BRANCH_TO_USE || $DRAFT =~ "true" ]]; then
  VERSION_REL=${THIS_BRANCH//$BRANCH_TO_USE/v}
  REL_TO_USE=$(echo "$RELEASES" | grep '"tag_name":' | sed -E 's/.*"([^"]+)".*/\1/' | sed -n "/$VERSION_REL/p" | sort -rV | head -n 1)
elif [[ "$THIS_BRANCH"  =~ "master" ]]; then
  # Get the latest release even if its a pre-release
  REL_TO_USE=$(echo "$RELEASES" | grep '"tag_name":' | sed -E 's/.*"([^"]+)".*/\1/' | sort -rV | head -n 1)
else
  REL_TO_USE=$LATEST_REL
fi

if [[ -z "$REL_TO_USE" ]]
then
  echo "An error has occurred trying to get the latest mmctl release. Aborting. Perhaps api.github.com is down, or you are being rate-limited.";
  echo "Set the GITHUB_USERNAME and GITHUB_TOKEN environment variables to the appropriate values to work around GitHub rate-limiting.";
  exit 1;
else
  echo "$REL_TO_USE"
fi