From 13dd243c8afe395922e3a3a6aab553b52ee51c11 Mon Sep 17 00:00:00 2001
From: Ed Morley <501702+edmorley@users.noreply.github.com>
Date: Mon, 25 Sep 2023 21:00:45 +0100
Subject: [PATCH] Set an explicit GitHub Actions shell

Setting an explicit bash shell ensures GitHub Actions enables pipefail
mode too, rather than only error on exit (due to GitHub Actions slightly
counter-intuitive choice of settings):
https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsshell

This is important for UX since this workflow uses pipes.

For example, without this change, if the `docker save` command here
fails, then the piping to zstd otherwise continues, resulting in an
empty exported images archive that will only fail much later in the
build when the archive is `docker load`ed. Such as seen here:
https://github.com/heroku/builder/actions/runs/6303703122/job/17113579563?pr=392#step:5:7

This shell is set globally, to avoid needing to specify it for every
job or run command:
https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#defaultsrun

GUS-W-14181209.
---
 .github/workflows/build-test-publish.yml | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/.github/workflows/build-test-publish.yml b/.github/workflows/build-test-publish.yml
index 6e0f6b0f..d27023a1 100644
--- a/.github/workflows/build-test-publish.yml
+++ b/.github/workflows/build-test-publish.yml
@@ -11,6 +11,13 @@ on:
 permissions:
   contents: read
 
+defaults:
+  run:
+    # Setting an explicit bash shell ensures GitHub Actions enables pipefail mode too, rather
+    # than only error on exit. This is important for UX since this workflow uses pipes. See:
+    # https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsshell
+    shell: bash
+
 jobs:
 
   create: