Automatically remind contributors to update their pull requests

So from my short professional experience, I have realised that if you are working with a small team of individuals a lot of folks end-up authoring multiple pull-requests across X different repositories in an organisation which sometimes leads to managing multiple feature PRs at a time.

This can sometimes leads to author forgetting to update their branches and test their code with the most stable (or latest) version possible. Since a lifetime of a pull request can be anything from 1 day to 1 week, its important to keep your branches up to date. But we developers forget to do this timely.

This is not a problem of just small teams, opensource projects (be it small or big) usually have this problem as well.

How to fix?

I went ahead and made a minimal github action to solve the above problem by reminding contributors to update their branches whenever base branch gets a new commit. We can do this by simply leaving a comment on pull requests (you can see a demo in the banner of this post)

Here is a simple workflow on how to setup this action

name: PR Update Reminder
on:
  push:
    branches:
      - main
      - dev

env:
  # make sure to set this as env
  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} 

jobs:
  remind_authors:
    runs-on: ubuntu-latest
    name: Update PR Reminder Test
    steps:
      - uses: actions/checkout@v2
      - uses: Bhupesh-V/update-pr-reminder-action@main

In the above workflow we are telling github to “watch” the main and dev branches of our repository for any new pushes and run the corressponding action. So what’ happening behind the scenes at update-pr-reminder-action?

We use a simple shell script combined with github’s CLI tool, gh and some some shell wizadry ✨

#!/bin/bash

all_open_prs=$(gh pr list --base "${GITHUB_REF#refs/*/}" --json author,number)
printf "%s\n" "PRs with base ${GITHUB_REF#refs/*/}: $all_open_prs"
prs_count=$(echo "$all_open_prs" | jq length)
printf "%s\n" "There are currently $prs_count open PRs"

for (( c=0; c<$prs_count; c++ )); do
    pr_id=$(echo "$all_open_prs" | jq .["$c"].number)
    author=$(echo "$all_open_prs" | jq .["$c"].author.login | tr -d '"')
    printf "%s\n" "Author for PR $pr_id is $author"
    gh pr comment $pr_id --body "Hey @$author 👋🏽 friendly reminder to update your PR/branch because there was a recent commit ($(git rev-parse HEAD)) to the base branch"
done

The first thing we need to do is find the current branch, which is done by ${GITHUB_REF#refs/*/} where GITHUB_REF is an environment variable which is set automatically in every github action

Next we find all the open PRs open using the gh tool

gh pr list --base main --json author,number

Note: gh needs to authenticate before you can use it, we have already done this by setting the env GITHUB_TOKEN. gh uses this token to make any API requests

This will return a json output of all the open PRs like this

[
  {
    "author": {
      "login": "Bhupesh-V"
    },
    "number": 400
  },
  {
    "author": {
      "login": "some-dev"
    },
    "number": 402
  },
  ...
 ] 

To parse json, we are using jq here,

# get pull request id
basename "$(echo "$all_open_prs" | jq .["$c"].number)"

Creating a comment is easy,

gh pr comment $pr_id --body "Comment body"

If you see the comment body in our action, we are also referencing the latest commit to base branch using git rev-parse HEAD

Hey @$author 👋🏽 friendly reminder to update your PR/branch because there was a recent merge ($(git rev-parse HEAD)) to the base branch

TODO

To reduce spam in case a pull request takes longer to get merged, we can also check if the branch is up to date by check if the base branches latest HEAD is present inside the authors PR

Closing Thoughts

Ideally this feature should exist alongside scheduled reminders nonetheless I believe its a good enough solution for now.

Resources

A bunch of resources that helped me write this workflow

• Using Github CLI in workflows
• jq cheatsheet