The code to handle printing of signature data from a struct
signature_check is very similar between verify-commit and verify-tag.
Place this in a single function. verify-tag retains its special case
behavior of printing the tag even when no valid signature is found.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>