content_id: no need to be human-friendly

We merely use this for internal comparisons and do not store
this in Xapian.  So using a shorter, non-human readable digest
is enough.  Furthermore, introduce "content_digest" which
returns the Digest::SHA object for extra changes.

1 files changed, 3 insertions, 2 deletions

diff --git a/t/content_id.t b/t/content_id.t
index c0ae6ecd..adcdb6c1 100644
--- a/t/content_id.t
+++ b/t/content_id.t
@@ -18,7 +18,8 @@ my $mime = Email::MIME->create(
         body => "hello world\n",
 );
 
-my $res = content_id($mime);
-like($res, qr/\ASHA-256:[a-f0-9]{64}\z/, 'cid in format expected');
+my $orig = content_id($mime);
+my $reload = content_id(Email::MIME->new($mime->as_string));
+is($orig, $reload, 'content_id matches after serialization');
 
 done_testing();