Add script to downstream PRs. (#39)

bin/downstream_pr.sh

+#!/bin/bash
+
+if [ -z "$1" ]
+  then
+    echo "Usage: downstream_pr.sh <PR_number>"
+    echo "Port a specified PR from the Aesara repo to the PyTensor repo. Will create a new branch, adapt and apply the upstream PR, and create a new PR to PyTensor."
+    exit 1
+fi
+
+set -e
+
+git checkout main
+git pull origin main
+git checkout -b downstream_$1
+
+echo "Downloading patch..."
+wget -O $1.patch https://patch-diff.githubusercontent.com/raw/aesara-devs/aesara/pull/$1.patch
+
+echo "Replacing aesara strings..."
+declare -a replace_strings=(
+    "s/aesara/pytensor/g"
+    "s/Aesara/PyTensor/g"
+)
+
+for replace in "${replace_strings[@]}"; do
+    sed -i -e "$replace" $1.patch
+done
+
+echo "Applying patch..."
+if git am -3 --reject $1.patch ; then
+    echo "Patch applied successfully..."
+else
+    echo "Patch failed. Find the .rej file and apply the changes manually. Then 'git add' all changed files, followed by 'git am --continue'. Then create a PR manually."
+    exit 1
+fi
+
+echo "Running pre-commit"
+pre-commit run --all
+
+git push origin downstream_$1
+# get the informative title
+title=$(curl https://api.github.com/repos/aesara-devs/aesara/pulls/$1 2>/dev/null | jq '.title')
+gh pr create --repo pymc-devs/pytensor --title "Downstreaming Aesara PR $1: $title" --body "Downstreaming https://github.com/aesara-devs/aesara/pull/$1. PR port done by downstream_pr.sh script."