From e6d194f95ed107e3bf75d110c64c7d7fcd1e3587 Mon Sep 17 00:00:00 2001
From: Ian Ker-Seymer <hello@ianks.com>
Date: Fri, 31 Jan 2025 22:37:40 -0500
Subject: [PATCH] Use deterministic SOURCE_DATE_EPOCH

---
 docker/setup/rb-sys-dock.sh |  2 +-
 gem/exe/rb-sys-dock         | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/docker/setup/rb-sys-dock.sh b/docker/setup/rb-sys-dock.sh
index 3573b8d7..d2ba924b 100755
--- a/docker/setup/rb-sys-dock.sh
+++ b/docker/setup/rb-sys-dock.sh
@@ -3,7 +3,7 @@
 set -e
 
 setup_sudoers() {
-  echo "Defaults        env_keep += \"BUNDLE_PATH RB_SYS_CARGO_TARGET_DIR RAKEOPT RUBY_TARGET\"" >> /etc/sudoers.d/rb-sys-dock
+  echo "Defaults        env_keep += \"BUNDLE_PATH RB_SYS_CARGO_TARGET_DIR RAKEOPT RUBY_TARGET GEM_PRIVATE_KEY_PASSPHRASE SOURCE_DATE_EPOCH\"" >> /etc/sudoers.d/rb-sys-dock
 }
 
 main() {
diff --git a/gem/exe/rb-sys-dock b/gem/exe/rb-sys-dock
index 6edd701f..ffb43faa 100755
--- a/gem/exe/rb-sys-dock
+++ b/gem/exe/rb-sys-dock
@@ -392,6 +392,7 @@ def rcd(input_args)
       -e RB_SYS_CARGO_TARGET_DIR=#{tmp_target_dir.inspect} \
       -e RUBY_CC_VERSION="#{ruby_versions}" \
       -e RUBY_TARGET="#{OPTIONS.fetch(:platform)}" \
+      -e SOURCE_DATE_EPOCH="#{source_date_epoch}" \
       -e RAKEOPT \
       -e TERM \
       -w #{working_directory} \
@@ -410,6 +411,19 @@ def rcd(input_args)
   exec(cmd)
 end
 
+def source_date_epoch
+  return ENV["SOURCE_DATE_EPOCH"] if ENV.key?("SOURCE_DATE_EPOCH")
+
+  stdout, status = Open3.capture2("git log -1 --pretty=%ct")
+
+  if status.success?
+    stdout.strip
+  else
+    logger.warn("Could not determine SOURCE_DATE_EPOCH from git log, using current time")
+    Time.now.to_i.to_s
+  end
+end
+
 def download_image
   image = ENV.fetch("RCD_IMAGE")