Adjust git_changelog for new-style release tags.

It wasn't on board with REL_n_n format.

src/tools/git_changelog

@@ -102,7 +102,8 @@ my %rel_tags;
 		{
 			my $commit = $1;
 			my $tag    = $2;
-			if (   $tag =~ /^REL\d+_\d+$/
+			if ($tag =~ /^REL_\d+_\d+$/
+			    || $tag =~ /^REL\d+_\d+$/
 			    || $tag =~ /^REL\d+_\d+_\d+$/)
 			{
 				$rel_tags{$commit} = $tag;
@@ -198,6 +199,7 @@ for my $branch (@BRANCHES)
 			$last_tag = $sprout_tags{$commit};
 
 			# normalize branch names for making sprout tags
+			$last_tag =~ s/^(REL_\d+).*/$1_BR/;
 			$last_tag =~ s/^(REL\d+_\d+).*/$1_BR/;
 		}
 		$c->{'last_tag'} = $last_tag;