Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/scripts/get_latest_release.sh

@@ -0,0 +1,57 @@
+#!/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