[CI/Build] Automate PR body text cleanup (#10082)

Signed-off-by: Russell Bryant <rbryant@redhat.com>

.github/scripts/cleanup_pr_body.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+set -eu
+
+# ensure 1 argument is passed
+if [ "$#" -ne 1 ]; then
+    echo "Usage: $0 <pr_number>"
+    exit 1
+fi
+
+PR_NUMBER=$1
+OLD=/tmp/orig_pr_body.txt
+NEW=/tmp/new_pr_body.txt
+
+gh pr view --json body --template "{{.body}}" "${PR_NUMBER}" > "${OLD}"
+cp "${OLD}" "${NEW}"
+
+# Remove all lines after and including "**BEFORE SUBMITTING, PLEASE READ THE CHECKLIST BELOW AND FILL IN THE DESCRIPTION ABOVE**"
+sed -i '/\*\*BEFORE SUBMITTING, PLEASE READ THE CHECKLIST BELOW AND FILL IN THE DESCRIPTION ABOVE\*\*/,$d' "${NEW}"
+
+# Remove "FIX #xxxx (*link existing issues this PR will resolve*)"
+sed -i '/FIX #xxxx.*$/d' "${NEW}"
+
+# Remove "FILL IN THE PR DESCRIPTION HERE"
+sed -i '/FILL IN THE PR DESCRIPTION HERE/d' "${NEW}"
+
+# Run this only if ${NEW} is different than ${OLD}
+if ! cmp -s "${OLD}" "${NEW}"; then
+    echo "Updating PR body"
+    gh pr edit --body-file "${NEW}" "${PR_NUMBER}"
+else
+    echo "No changes needed"
+fi