[debhelper-devel] [debhelper] 01/02: Define SOURCE_DATE_EPOCH when setting build flags

[Niels Thykier]

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nthykier pushed a commit to branch master
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commit d9ea95e44a83d9f9288b720fbb15b4d8156fd550
Author: Dhole <dhole at openmailbox.org>
Date:   Thu Jul 2 17:16:13 2015 +0200

    Define SOURCE_DATE_EPOCH when setting build flags
    
    When SOURCE_DATE_EPOCH is defined software which needs a timestamp can use it
    as a reference date instead of the current date and time. For more details,
    see: https://wiki.debian.org/ReproducibleBuilds/TimestampsProposal
    
    The variable is set alongside other build flags, and its value is the time
    of the latest entry in `debian/changelog`.
    
    Closes: #791823
---
 Debian/Debhelper/Dh_Lib.pm | 32 +++++++++++++++++++++++++++++++-
 debian/changelog           |  7 +++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/Debian/Debhelper/Dh_Lib.pm b/Debian/Debhelper/Dh_Lib.pm
index 348144e..c5b2748 100644
--- a/Debian/Debhelper/Dh_Lib.pm
+++ b/Debian/Debhelper/Dh_Lib.pm
@@ -1143,12 +1143,42 @@ sub cross_command {
 	}
 }
 
+# Read latest debian/changelog timestamp and export the environment
+# variable SOURCE_DATE_EPOCH with its value, so that any package can
+# read it and replace calls to localtime (or other undeterministic
+# timestamps) with the exported timestamp to get reproducible builds.
+sub set_source_date_epoch {
+	eval "use Dpkg::Changelog::Debian";
+	if ($@) {
+		warning "unable to set SOURCE_DATE_EPOCH: $@";
+		return;
+	}
+	eval "use Time::Piece";
+	if ($@) {
+		warning "unable to set SOURCE_DATE_EPOCH: $@";
+		return;
+	}
+
+	my $changelog = Dpkg::Changelog::Debian->new();
+	$changelog->load("debian/changelog");
+
+	my $tt = @{$changelog}[0]->get_timestamp();
+	$tt =~ s/\s*\([^\)]+\)\s*$//; # Remove the optional timezone codename
+	my $timestamp = Time::Piece->strptime($tt, "%a, %d %b %Y %T %z");
+
+	$ENV{SOURCE_DATE_EPOCH} = $timestamp->epoch();
+}
+
 # Sets environment variables from dpkg-buildflags. Avoids changing
 # any existing environment variables.
 sub set_buildflags {
-	return if $ENV{DH_INTERNAL_BUILDFLAGS} || compat(8);
+	return if $ENV{DH_INTERNAL_BUILDFLAGS};
 	$ENV{DH_INTERNAL_BUILDFLAGS}=1;
 
+	set_source_date_epoch();
+
+	return if compat(8);
+
 	eval "use Dpkg::BuildFlags";
 	if ($@) {
 		warning "unable to load build flags: $@";
diff --git a/debian/changelog b/debian/changelog
index ef4455b..2cfd1a1 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,10 @@
+debhelper (9.20150811+unreleased) UNRELEASED; urgency=medium
+
+  * dh/dh_auto_*: Apply patch from "Dhole" to define
+    SOURCE_DATE_EPOCH.  (Closes: #791823)
+
+ -- Niels Thykier <niels at thykier.net>  Wed, 12 Aug 2015 10:46:59 +0200
+
 debhelper (9.20150811) unstable; urgency=medium
 
   * d/changelog: Add missing entry for dh_md5sums/#786695 in

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