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