check *_source.changes if they are valid debian source change files

Without this commit all *.changes files are checked like changelog files

With this commit 40-sequence-changes checks if the file is a valid debian
source changes file when the filename matches *_source.changes, by searching
for all mandatory keywords in the file. If it is a valid debian source
changes file, further changelog checks are ommitted

Fixes #42

40-sequence-changes

@@ -15,6 +15,10 @@ FIRST_CHANGES=""
 RETURN=0
 for i in $DIR_TO_CHECK/*.changes ; do
     test -f $i || continue
+    if [ $i != ${i%_source.changes} ];then
+      /usr/lib/obs/service/source_validators/helpers/check_debian_source_changes $i && continue
+      echo "(W) File ends with '_source.changes' but is not a valid debian source changes file"
+    fi
     RETURN=0
     test -n "$FIRST_CHANGES" || FIRST_CHANGES=$i
     if test -n "$FIRST_CHANGES" -a "$FIRST_CHANGES" != "$i" ; then

helpers/DebianSourceChangesValidator.pm

@@ -0,0 +1,21 @@
+package DebianSourceChangesValidator;
+
+use strict;
+use warnings;
+
+sub validate {
+  my ($fname) = @_;
+  my @mandatory = qw/Format Date Source Binary Architecture Version Distribution Maintainer Description Changes Checksums-Sha1 Checksums-Sha256 Files/;
+  my $re    = '^('.join('|',@mandatory).'):.*';
+  my $result = {};
+
+  open(my $fh,$fname) || die "Could not open '$fname': $!\n";
+  while (my $line = <$fh>) { $line =~ m/$re/ && $result->{$1}++ }
+  close $fh;
+
+  for my $key (@mandatory) { return 1 if (! $result->{$key} ) }
+
+  return 0
+}
+
+1;

helpers/check_debian_source_changes

@@ -0,0 +1,12 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+BEGIN { unshift(@::INC,'/usr/lib/obs/service/source_validators/helpers/') }
+
+use DebianSourceChangesValidator;
+
+my $ev = DebianSourceChangesValidator::validate($ARGV[0]);
+
+exit $ev;