feat: barretenberg PR migrate tool

scripts/migrate_barretenberg_branch.sh

@@ -0,0 +1,56 @@
+#!/bin/bash
+set -eu
+
+# Usage: ./this.sh <branch> <commit_message>
+# Script for migrating PRs from barretenberg repo to aztec-packages.
+# Meant to be used from master with a branch name that exists on barretenberg repo but not aztec-packages.
+# You can change the commit message after with git commit --amend if needed.
+
+# Display usage if not enough arguments
+if [ "$#" -ne 2 ]; then
+    echo "Usage: $0 <branch> <commit_message>"
+    exit 1
+fi
+
+# Check for unstaged changes
+if ! git diff-index --quiet HEAD --; then
+    echo "Error: You have unstaged changes. Please commit or stash them before running git_subrepo.sh."
+    exit 1
+fi
+
+BRANCH="$1"
+COMMIT_MESSAGE="$2"
+SUBREPO_PATH=circuits/cpp/barretenberg # can be changed to another subrepo if useful
+
+SCRIPT_DIR=$(dirname "$(realpath "$0")")
+cd "$SCRIPT_DIR"/..
+
+echo "(branch migrate) Switching to a new branch named '$BRANCH' (this branch can't already exist)"
+
+# Check if branch already exists
+if git rev-parse --verify "$BRANCH" >/dev/null 2>&1; then
+    echo "Error: Aztec branch '$BRANCH' already exists. Please delete it with 'git branch -D $BRANCH' if you are sure you don't need it."
+    exit 1
+fi
+
+git checkout -b "$BRANCH"
+
+echo "(branch migrate) Pulling from upstream barretenberg repo. If this doesn't work, your barretenberg branch may need to merge barretenberg master."
+# note: we use force with the assumption that people don't care about their subrepo stash branch
+if ! scripts/git_subrepo.sh pull "$SUBREPO_PATH" --branch=$BRANCH --force; then
+    echo "Error: Failed to pull from upstream barretenberg repo. Check your branch name or network connection."
+    exit 1
+fi
+
+echo "(branch migrate) Automatic git data fix"
+# Tosses away the .gitrepo changes, as those we only want if pulling from barretenberg master, not PRs (which will go in as aztec commits).
+# because git-subrepo uses 'git rm -r', we fix up .gitmodules after as well. This is an edge-case gotcha using 
+# git submodules along with git-subrepo.
+
+git checkout HEAD^ -- "$SUBREPO_PATH"/.gitrepo .gitmodules
+
+if ! git commit --amend -m "$COMMIT_MESSAGE"; then
+    echo "Error: Failed to commit changes. Check your commit message."
+    exit 1
+fi
+echo "(branch migrate) All done. You can now 'git push origin HEAD' and click to create a PR on aztec. Changes will then automatically go into barretenberg when merged."