From 089bd14d64e0fa277ee9bcc6e28f9c18c9004752 Mon Sep 17 00:00:00 2001
From: Weiqun Zhang <weiqunzhang@lbl.gov>
Date: Fri, 15 May 2026 21:55:15 -0700
Subject: [PATCH] Sphinx build: Stabilize PDF metadata across builds

Setting SOURCE_DATE_EPOCH before make latexpdf so pdfTeX produces
byte-identical amrex.pdf when the documentation source hasn't changed,
avoiding a new ~7 MB blob in git on every deploy.  The fixed epoch
(441763200 = 1984-01-01 UTC) pins CreationDate, ModDate, and /ID.
---
 build_docs.sh | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/build_docs.sh b/build_docs.sh
index eccf6de9e24..d19b617c3cc 100755
--- a/build_docs.sh
+++ b/build_docs.sh
@@ -27,6 +27,9 @@ cd ..
 # Build sphinx
 cd Docs/sphinx_documentation
 echo "Build the Sphinx documentation for Amrex."
+# Stabilize PDF metadata (CreationDate, ModDate, /ID) so identical
+# content produces byte-identical output across repeated builds.
+export SOURCE_DATE_EPOCH=441763200 # 1984-01-01 UTC
 make PYTHON="python3" latexpdf
 mv build/latex/amrex.pdf source/
 make clean