updated github_merge_branch.sh

github_merge_branch.sh

@@ -56,8 +56,10 @@ max_args 3 "$@"
 output="$("$srcdir/github_pull_request_create.sh" "$@")"
 
 if [ -n "$output" ]; then
-    pr_url="$(grep '/pull/' <<< "$output" || die "Failed to generate Pull Request or couldn't find pull URL in output")"
-    timestamp "Merging Pull Request $pr_url"
-    gh pr merge --merge "$pr_url"
+    # defined in lib/github.sh
+    # shellcheck disable=SC2154
+    url="$(grep -Eom1 "$github_pull_request_url_regex" <<< "$output" || die "Failed to generate Pull Request or couldn't find pull request URL in output")"
+    timestamp "Merging Pull Request $url"
+    gh pr merge --merge "$url"
     echo >&2
 fi