Update auto-merge action to use bash script (#3595)

* Add bash script for merging PRs

Signed-off-by: Ankita Katiyar <ankitakatiyar2401@gmail.com>

* Remove labeler action

Signed-off-by: Ankita Katiyar <ankitakatiyar2401@gmail.com>

---------

Signed-off-by: Ankita Katiyar <ankitakatiyar2401@gmail.com>

.github/workflows/auto-merge-prs.yml

@@ -9,12 +9,18 @@ on:
 
 jobs:
   automerge:
-    permissions:
-      pull-requests: read
-      contents: write
     runs-on: ubuntu-latest
     steps:
-      - name: Automerge PRs with "automerge" label
-        uses: "pascalgn/automerge-action@v0.16.2"
-        env:
-          GITHUB_TOKEN: "${{ secrets.GH_TAGGING_TOKEN }}"
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.GH_TAGGING_TOKEN }}
+
+      - name: Set git email and name
+        run: |
+          git config --global user.email "kedro@kedro.com"
+          git config --global user.name "Kedro"
+
+      - name: Maybe merge automerge PR to `develop`
+        run: ./tools/github_actions/attempt_merge_pr.sh "merge-main-to-develop" "develop" ${{ secrets.GH_TAGGING_TOKEN }}

tools/github_actions/attempt_merge_pr.sh

@@ -0,0 +1,97 @@
+#!/usr/bin/env bash
+# Script to attempt to merge an automatic PR from main to develop.
+
+# Exit script if you try to use an uninitialized variable.
+set -o nounset
+
+# Exit script if a statement returns a non-true return value.
+set -o errexit
+
+SOURCE_BRANCH=$1
+TARGET_BRANCH=$2
+GITHUB_TAGGING_TOKEN=$3
+GITHUB_USER="kedro-org"
+GITHUB_REPO="kedro"
+
+# Array of GitHub mergeable states that are valid to proceed with automatic PR merging.
+# Adding "unstable" can be convenient, as it allows to auto-merge pull requests that
+# pass just the required CI checks (whereas "clean" requires all CI checks to pass,
+# regardless of whether they are required or not). More info:
+# https://docs.github.com/en/graphql/reference/enums#mergestatestatus
+# https://github.com/octokit/octokit.net/issues/1763
+VALID_MERGEABLE_STATES=("clean" "unstable")
+
+find_github_pr() {
+  # Find a PR from source to target branch
+  # Returns PR number if GitHub returned exactly one such PR
+  endpoint="https://api.github.com/repos/${GITHUB_USER}/${GITHUB_REPO}/pulls?base=${TARGET_BRANCH}&head=${GITHUB_USER}:${SOURCE_BRANCH}&state=open"
+  response=$(curl --silent --header "Authorization: token ${GITHUB_TAGGING_TOKEN}" "${endpoint}")
+  num_open_prs=$(echo "$response" | tr '\r\n' ' ' | jq "length")
+  if [ "$num_open_prs" -eq 1 ]; then
+    echo "$response" | tr '\r\n' ' ' | jq ".[0].number"
+  fi
+}
+
+check_pr_mergeable() {
+  # Check that the given PR is in a mergeable state
+  pr=$1
+  endpoint="https://api.github.com/repos/${GITHUB_USER}/${GITHUB_REPO}/pulls/${pr}"
+  response=$(curl --silent --header "Authorization: token ${GITHUB_TAGGING_TOKEN}" "${endpoint}")
+  mergeable=$(echo "${response}" | tr '\r\n' ' ' | jq ".mergeable // false")  # default to false
+  echo "PR ${pr} mergeable: ${mergeable}"
+  mergeable_state=$(echo "${response}" | tr '\r\n' ' ' | jq --raw-output ".mergeable_state // \"unknown\"")
+  echo "PR ${pr} mergeable_state: ${mergeable_state}"
+  [ "${mergeable}" == true ] && [[ " ${VALID_MERGEABLE_STATES[@]} " =~ " ${mergeable_state} " ]]
+}
+
+toggle_merge_commits() {
+  # Turns merge commits on or off for the repository
+  allow_merge_commit=$1
+  endpoint="https://api.github.com/repos/${GITHUB_USER}/${GITHUB_REPO}"
+  payload="{\"allow_merge_commit\": ${allow_merge_commit}}"
+  status_code=$(curl -X PATCH \
+    --silent \
+    --header "Authorization: token ${GITHUB_TAGGING_TOKEN}" \
+    --header "Content-Type: application/json" \
+    --data "${payload}" \
+    --output /dev/null \
+    --write-out "%{http_code}\n" \
+    "${endpoint}")
+  [ "${status_code}" -eq 200 ]
+}
+
+merge_pr() {
+  # Merge a given PR using merge commit
+  pr=$1
+  toggle_merge_commits true
+  endpoint="https://api.github.com/repos/${GITHUB_USER}/${GITHUB_REPO}/pulls/${pr}/merge"
+  payload='{"merge_method": "merge"}'
+  response=$(curl -X PUT \
+    --silent \
+    --header "Authorization: token ${GITHUB_TAGGING_TOKEN}" \
+    --header "Content-Type: application/json" \
+    --data "${payload}" \
+    "${endpoint}")
+  toggle_merge_commits false
+  merged=$(echo "${response}" | tr '\r\n' ' ' | jq ".merged // false")  # default to false
+  if [ "${merged}" == true ]; then
+    echo "PR ${pr} successfully merged"
+  else
+    message=$(echo "${response}" | tr '\r\n' ' ' | jq --raw-output ".message")
+    echo "PR ${pr} NOT merged. Message: ${message}"
+  fi
+  [ "${merged}" == true ]
+}
+
+pr_number=$(find_github_pr)
+
+if [ -z "${pr_number}" ]; then
+  echo "No PR found from ${SOURCE_BRANCH} to ${TARGET_BRANCH}"
+  exit 0
+fi
+
+if check_pr_mergeable "${pr_number}"; then
+  merge_pr "${pr_number}"
+else
+  echo "PR ${pr_number} is not in a mergeable state"
+fi