Merge branch 'bc/gpg-verify-raw'

"git verify-tag" and "git verify-commit" have been taught to share
more code, and then learned to optionally show the verification
message from the underlying GPG implementation.

* bc/gpg-verify-raw:
verify-tag: add option to print raw gpg status information
verify-commit: add option to print raw gpg status information
gpg: centralize printing signature buffers
gpg: centralize signature check
verify-commit: add test for exit status on untrusted signature
verify-tag: share code with verify-commit
verify-tag: add tests

diff --cc commit.c
Simple merge

diff --cc commit.h
Simple merge