From 158f28dd36f0c01e257f8e7657e51fde4b62dcdb Mon Sep 17 00:00:00 2001
From: Jeremy Massel <1123407+jkmassel@users.noreply.github.com>
Date: Tue, 26 May 2026 15:15:02 -0600
Subject: [PATCH] ci: replace bash 4 mapfile with portable while-read loop
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`mapfile` is a Bash 4+ builtin. The `Clean up pr-build/*` step runs on
the `mac` queue, where macOS ships Bash 3.2 — so the script aborts at
line 25 with `mapfile: command not found` (exit 127), failing every
trunk build.

Replace with a `while IFS= read -r ... done < <(...)` loop, which is
equivalent under both Bash 3.2 and 4+.

Build that surfaced this:
https://buildkite.com/automattic/gutenbergkit/builds/2360
---
 .buildkite/cleanup-pr-build-branches.sh | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/.buildkite/cleanup-pr-build-branches.sh b/.buildkite/cleanup-pr-build-branches.sh
index 13db49b6b..69b4ddeec 100755
--- a/.buildkite/cleanup-pr-build-branches.sh
+++ b/.buildkite/cleanup-pr-build-branches.sh
@@ -22,7 +22,12 @@ echo '--- :robot_face: Use bot for Git operations'
 source use-bot-for-git
 
 echo "--- :mag: Listing pr-build/* branches on origin"
-mapfile -t branches < <(
+# `mapfile` is Bash 4+; macOS CI agents ship Bash 3.2, so use a portable
+# `while read` loop instead.
+branches=()
+while IFS= read -r branch; do
+    branches+=("$branch")
+done < <(
     git ls-remote --heads origin 'refs/heads/pr-build/*' \
         | awk '{print $2}' \
         | sed 's|^refs/heads/||'