From 643d772babb9886f6a1c0d0944c008e52cfdb259 Mon Sep 17 00:00:00 2001
From: Austin Seipp <aseipp@pobox.com>
Date: Tue, 5 Nov 2024 23:34:59 -0600
Subject: [PATCH] github: cancel in-progress builds on stale PRs

When a pull request is pushed multiple times in sequence (e.g. to fix small
errors that are noticed post-submission), a backlog of builds ends up needing
to be cleared out before your new update can be built. If you push N times, N
builds are queued and need to clear out first.

This can cause higher latency for *every* PR since the pool of public runners
is shared, and in general seems uneconomical and inefficient since 99% of the
time you want to build the new version ASAP.

Luckily GHA has a universal solution to this: use the `concurrency` directive
to group all builds for a PR under a name, and when a new build appears in that
group, cancel all builds in the group that are in-progress.

Taken from this useful blog post: "Simple trick to save environment and money
when using GitHub Actions"

https://turso.tech/blog/simple-trick-to-save-environment-and-money-when-using-github-actions

Signed-off-by: Austin Seipp <aseipp@pobox.com>
---
 .github/workflows/build-nix.yml  | 4 ++++
 .github/workflows/build.yml      | 4 ++++
 .github/workflows/codespell.yml  | 4 ++++
 .github/workflows/dependabot.yml | 4 ++++
 4 files changed, 16 insertions(+)

diff --git a/.github/workflows/build-nix.yml b/.github/workflows/build-nix.yml
index 380c67a94e..73f1fb4a84 100644
--- a/.github/workflows/build-nix.yml
+++ b/.github/workflows/build-nix.yml
@@ -6,6 +6,10 @@ on:
       - main
   pull_request:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 permissions: read-all
 
 jobs:
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 118f48a702..2447c7f8de 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -4,6 +4,10 @@ on:
   push:
   pull_request:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 permissions: read-all
 
 env:
diff --git a/.github/workflows/codespell.yml b/.github/workflows/codespell.yml
index 03e097c028..37870813be 100644
--- a/.github/workflows/codespell.yml
+++ b/.github/workflows/codespell.yml
@@ -6,6 +6,10 @@ on:
       - main
   pull_request:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 permissions: read-all
 
 jobs:
diff --git a/.github/workflows/dependabot.yml b/.github/workflows/dependabot.yml
index 41ccb0598a..7b935d2e98 100644
--- a/.github/workflows/dependabot.yml
+++ b/.github/workflows/dependabot.yml
@@ -3,6 +3,10 @@ name: Enable auto-merge for Dependabot PRs
 on:
   pull_request:
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 permissions: read-all
 
 jobs: