Add a local perl module to get year last changed

This is used for generating a more-correct copyright statement
for the "build_generated" targets.

Fixes: #13765

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/13791)

1 files changed, 43 insertions, 0 deletions

diff --git a/util/perl/OpenSSL/copyright.pm b/util/perl/OpenSSL/copyright.pm
new file mode 100644
index 0000000000..1fd9f353f7
--- /dev/null
+++ b/util/perl/OpenSSL/copyright.pm
@@ -0,0 +1,43 @@
+#! /usr/bin/env perl
+# Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the Apache License 2.0 (the "License").  You may not use
+# this file except in compliance with the License.  You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+
+use strict;
+use warnings;
+
+package OpenSSL::copyright;
+
+sub year_of {
+    my $file = shift;
+
+    return $ENV{'OSSL_COPYRIGHT_YEAR'} if defined $ENV{'OSSL_COPYRIGHT_YEAR'};
+
+    # Get the current year.  We use that as the default because the other
+    # common case is that someone unpacked a tarfile and the file dates
+    # are't properly set on extract.
+    my $YEAR = [localtime()]->[5] + 1900;
+
+    # See if git's available
+    open my $FH,
+       "git log -1 --date=format:%Y --format=format:%ad $file 2>/dev/null|"
+           or return $YEAR;
+    my $LINE = <$FH>;
+    close $FH;
+    chomp($LINE);
+    $YEAR = $LINE if $LINE;
+    return $YEAR;
+}
+
+sub latest {
+    my $l = 0;
+    foreach my $f (@_ ) {
+        my $y = year_of($f);
+        $l = $y if $y > $l;
+    }
+    return $l
+}
+1;