From: intrigeri <intrigeri@boum.org>
Date: Mon, 27 Jun 2016 13:23:53 +0000
Subject: Honour SOURCE_DATE_EPOCH for embedded timestamp in generated
 documentation.

When the environment variable SOURCE_DATE_EPOCH is set, use it instead of the
current time for the embedded build timestamp.

The specification of SOURCE_DATE_EPOCH is available here:
https://reproducible-builds.org/specs/source-date-epoch/

In the case it is not defined, fall back to current time.
---
 lib/Command/V1.pm              | 2 +-
 lib/Command/View/DocMethods.pm | 2 +-
 lib/UR/Context.pm              | 8 ++++++++
 3 files changed, 10 insertions(+), 2 deletions(-)

--- a/lib/Command/V1.pm
+++ b/lib/Command/V1.pm
@@ -598,7 +598,7 @@ sub doc_sections {
     my $command_name = $self->command_name;
     my $version = do { no strict; ${ $self->class . '::VERSION' } };
     my $help_brief = $self->help_brief;
-    my $datetime = $self->__context__->now;
+    my $datetime = $self->__context__->build_time;
     my $sub_commands = $self->help_sub_commands(brief => 1) if $self->is_sub_command_delegator;
     my ($date,$time) = split(' ',$datetime);
 
--- a/lib/Command/View/DocMethods.pm
+++ b/lib/Command/View/DocMethods.pm
@@ -168,7 +168,7 @@ sub doc_sections {
 
     my $version = do { no strict; ${ $self->class . '::VERSION' } };
     my $help_brief = $self->help_brief;
-    my $datetime = $self->__context__->now;
+    my $datetime = $self->__context__->build_time;
     my ($date,$time) = split(' ',$datetime);
 
     push(@sections, UR::Doc::Section->create(
--- a/lib/UR/Context.pm
+++ b/lib/UR/Context.pm
@@ -137,6 +137,14 @@ sub now {
     return Date::Format::time2str(date_template(), time());
 }
 
+sub build_time {
+    return Date::Format::time2str(
+        date_template(),
+        $ENV{SOURCE_DATE_EPOCH} || time(),
+        'UTC'
+    );
+}
+
 my $master_monitor_query = 0;
 sub monitor_query {
     return if $UR::Object::Type::bootstrapping;