From 2accea2c81353263d2ce8a0cc3f97af266d0dd9c Mon Sep 17 00:00:00 2001
From: Jasper Van der Jeugt <m@jaspervdj.be>
Date: Fri, 2 Dec 2016 11:14:56 +0100
Subject: [PATCH] Read SOURCE_DATE_EPOCH if it exists

---
 Makefile          | 5 +++--
 extra/make-man.hs | 3 +--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index a67b77a..4e932fb 100644
--- a/Makefile
+++ b/Makefile
@@ -1,8 +1,9 @@
 PANDOC_MINOR_VERSION=$(shell ghc-pkg latest pandoc | sed 's/.*-//' | cut -d. -f2)
-PATAT_BUILD_DATE=$(shell date '+%B %d, %Y' -d "$(shell git log -1 --format=%cd --date=short)")
+SOURCE_DATE_EPOCH?=$(shell git log -1 --format=%cd --date=unix)
+SOURCE_DATE=$(shell date '+%B %d, %Y' -d "@${SOURCE_DATE_EPOCH}")
 
 extra/patat.1: README.md extra/make-man
-	PATAT_BUILD_DATE="$(PATAT_BUILD_DATE)" ./extra/make-man >$@
+	SOURCE_DATE="$(SOURCE_DATE)" ./extra/make-man >$@
 
 extra/make-man: extra/make-man.hs
 	ghc -DPANDOC_MINOR_VERSION=${PANDOC_MINOR_VERSION} -Wall -o $@ $<
diff --git a/extra/make-man.hs b/extra/make-man.hs
index d358101..bb29131 100644
--- a/extra/make-man.hs
+++ b/extra/make-man.hs
@@ -83,9 +83,8 @@ main = do
     Right pandoc0  <- Pandoc.readMarkdown Pandoc.def <$> readFile "README.md"
     Right template <- Pandoc.getDefaultTemplate Nothing "man"
 
-    -- It's important for reproducible builds that we get the date from git.
     version <- getVersion
-    date    <- getEnv "PATAT_BUILD_DATE"
+    date    <- getEnv "SOURCE_DATE"
 
     let writerOptions = Pandoc.def {
 #if PANDOC_MINOR_VERSION >= 19