The GitHub API supports the ability to add comments to open Pull Requests. With this in mind you can utilize environment variables and a cURL to automatically update/comment on a PR.
This could be utilized for reporting data collected during builds running on CircleCI, such as overall test coverage stats.
The first step would be to setup a new personal token for a user who will be making the comments, this could be you (the admin on the account) or a new bot user. Then set the username of who will make comments and the personal token as project-level environment variables.
Once that is complete you can add a new step that will check for an Open PR and post a comment to it:
name: Post Stats to GitHub PR
sudo apt-get install jq
pr_response=$(curl --location --request GET "https://api.github.com/repos/$CIRCLE_PROJECT_USERNAME/$CIRCLE_PROJECT_REPONAME/pulls?head=$CIRCLE_PROJECT_USERNAME:$CIRCLE_BRANCH&state=open" \
if [ $(echo $pr_response | jq length) -eq 0 ]; then
echo "No PR found to update"
pr_comment_url=$(echo $pr_response | jq -r ".._links.comments.href")
curl --location --request POST "$pr_comment_url" \
-u $GH_USER:$GH_TOKEN \
--header 'Content-Type: application/json' \
"body": "This would be the data to add"
Last step is to replace the "This would be the data to add" with the content you want added as a comment.