build: add SOURCE_DATE_EPOCH support

Author: flowerysong

configure.ac

@@ -375,8 +375,14 @@ test "x$prefix" = xNONE && prefix=$ac_default_prefix
 SYSCONFDIR=`eval echo "$sysconfdir"`
 AC_SUBST([SYSCONFDIR])
 
-BUILDDATE=`date +%F`
-AC_SUBST([BUILDDATE])
+AS_IF([test "x$SOURCE_DATE_EPOCH" = x], [
+    SOURCE_DATE_EPOCH=`git log -1 --pretty=%ct 2>/dev/null`
+])
+AS_IF([test "x$SOURCE_DATE_EPOCH" = x], [
+    SOURCE_DATE_EPOCH=`date +%s 2>/dev/null`
+])
+BUILD_DATE=`date -d @$SOURCE_DATE_EPOCH +%F 2>/dev/null`
+AC_SUBST([BUILD_DATE])
 
 #
 # Finish up

contrib/openarc-keygen.1.in

@@ -1,6 +1,6 @@
 .\" Copyright 2024 OpenARC contributors.
 .\" See LICENSE.
-.Dd @BUILDDATE@
+.Dd @BUILD_DATE@
 .Dt OPENARC-KEYGEN 1
 .Os OpenARC @VERSION@
 

openarc/openarc.8.in

@@ -2,7 +2,7 @@
 .\" reserved. See LICENSE.Sendmail.
 .\" Copyright (c) 2009-2013, 2015, 2016, The Trusted Domain Project. All
 .\" rights reserved. See LICENSE.
-.Dd @BUILDDATE@
+.Dd @BUILD_DATE@
 .Dt OPENARC 8
 .Os OpenARC @VERSION@
 

openarc/openarc.conf.5.in

@@ -2,7 +2,7 @@
 .\" reserved. See LICENSE.Sendmail.
 .\" Copyright (c) 2009-2017, The Trusted Domain Project. All rights reserved.
 .\" See LICENSE.
-.Dd @BUILDDATE@
+.Dd @BUILD_DATE@
 .Dt OPENARC.CONF 5
 .Os OpenARC @VERSION@