Adds automation script to add issue label

Signed-off-by: Darshit Chanpura <dchanp@amazon.com>

.github/actions/copy-issue-labels-to-pr.py

@@ -0,0 +1,67 @@
+#!/usr/bin/python3
+# SPDX-License-Identifier: Apache-2.0
+
+import itertools
+import json
+import re
+import sys
+from github import Github
+
+# We don't want to copy all labels on linked issues; only those in this subset.
+COPYABLE_LABELS = {
+  "enhancement",
+  "documentation"
+}
+
+# Returns a pull request extracted from Github's event JSON.
+def get_pr(event):
+    # --- Extract PR from event JSON ---
+    # `check_run`/`check_suite` does not include any direct reference to the PR
+    # that triggered it in its event JSON. We have to extrapolate it using the head
+    # SHA that *is* there.
+
+    # Get head SHA from event JSON
+    pr_head_sha = event["check_suite"]["head_sha"]
+
+    # Find the repo PR that matches the head SHA we found
+    return {pr.head.sha: pr for pr in repo.get_pulls()}[pr_head_sha]
+
+# Get all issue numbers related to a PR.
+def get_related_issues(pr):
+    # Regex to pick out closing keywords.
+    regex = re.compile("(close[sd]?|fix|fixe[sd]?|resolve[sd]?)\s*:?\s+#(\d+)", re.I)
+
+    # Extract all associated issues from closing keyword in PR
+    for verb, num in regex.findall(pr.body):
+        yield int(num)
+
+    # Extract all associated issues from PR commit messages
+    for c in pr.get_commits():
+        for verb, num in regex.findall(c.commit.message):
+            yield int(num)
+
+# Get inputs from shell
+(token, repository, path) = sys.argv[1:4]
+
+# Initialize repo
+repo = Github(token).get_repo(repository)
+
+# Open Github event JSON
+with open(path) as f:
+    event = json.load(f)
+
+# Get the PR we're working on.
+pr = get_pr(event)
+pr_labels = {label.name for label in pr.labels}
+
+# Get every label on every linked issue.
+issues = get_related_issues(pr)
+issues_labels = [repo.get_issue(n).labels for n in issues]
+issues_labels = {l.name for l in itertools.chain(*issues_labels)}
+
+# Find the set of all labels we want to copy that aren't already set on the PR.
+unset_labels = COPYABLE_LABELS & issues_labels - pr_labels
+
+# If there are any labels we need to add, add them.
+if len(unset_labels) > 0:
+    pr.set_labels(*list(unset_labels))

.github/workflows/apply-issue-labels-to-pr.yml

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+name: Apply issue labels to PR
+
+on:
+  pull_request:
+  pull_request_target:
+
+jobs:
+  mirror-labels-to-pr:
+#    if: github.repository == 'opensearch-project/OpenSearch'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Run label script
+        run: ../actions/copy-issue-labels-to-pr.py ${{ secrets.GITHUB_TOKEN }} $GITHUB_REPOSITORY $GITHUB_EVENT_PATH