my $usage = "Usage: $0 commit-diff -r<revision> ".
"<tree-ish> <tree-ish> [<URL>]";
fatal($usage) if (!defined $ta || !defined $tb);
my $usage = "Usage: $0 commit-diff -r<revision> ".
"<tree-ish> <tree-ish> [<URL>]";
fatal($usage) if (!defined $ta || !defined $tb);