Github Action to check deprecations in PR (#19666)

* deprecation check

* adding script

* add execute permission to script

* revert changes

* adding the script back

* added working script for local and GHA

* give execute permissions

* updating revgrep

* adding changes to script, tools

* run go mod tidy

* removing default ref

* make bootstrap

* adding to makefile

scripts/deprecations-checker.sh

@@ -0,0 +1,52 @@
+# Copyright (c) HashiCorp, Inc.
+# SPDX-License-Identifier: MPL-2.0
+
+# This script is sourced into the shell running in a Github Actions workflow.
+
+# Usage:
+# To check deprecations locally using the script, follow these steps:
+# From the repository root or within a package folder, execute deprecations-checker.sh 
+# Optionally: to only show deprecations in changed files between the current branch and 
+# a specific branch, pass the other branch name as an argument to the script.
+#
+# For example: 
+# ./scripts/deprecations-checker.sh (or) make deprecations
+# ./scripts/deprecations-checker.sh main (or) make ci-deprecations
+#
+# If no branch name is specified, the command will show all usage of deprecations in the code.
+#
+# GitHub Actions runs this against the PR's base ref branch. 
+
+# Staticcheck uses static analysis to finds bugs and performance issues, offers simplifications, 
+# and enforces style rules.
+# Here, it is used to check if a deprecated function, variable, constant or field is used.
+
+# Run staticcheck 
+echo "Performing deprecations check: running staticcheck"
+
+# Identify repository name
+if [ -z $2 ]; then
+    # local repository name
+    repositoryName=$(basename `git rev-parse --show-toplevel`)
+else
+    # github repository name from deprecated-functions-checker.yml
+    repositoryName=$2
+fi
+
+# Modify the command with the correct build tag based on repository
+if [ $repositoryName == "vault-enterprise" ]; then
+    staticcheckCommand=$(echo "staticcheck ./... -tags=enterprise")
+else
+    staticcheckCommand=$(echo "staticcheck ./...")
+fi
+
+# If no compare branch name is specified, output all deprecations
+# Else only output the deprecations from the changes added
+if [ -z $1 ]
+    then
+        $staticcheckCommand | grep deprecated
+    else
+        # GitHub Actions will use this to find only changes wrt PR's base ref branch
+        # revgrep CLI tool will return an exit status of 1 if any issues match, else it will return 0
+        $staticcheckCommand | grep deprecated 2>&1 | revgrep "$(git merge-base HEAD "origin/$1")"
+fi