Merge branch 'sg/gpg-sig'

Teach "merge/pull" to optionally verify and reject commits that are not signed properly. * sg/gpg-sig: pretty printing: extend %G? to include 'N' and 'U' merge/pull Check for untrusted good GPG signatures merge/pull: verify GPG signatures of commits being merged commit.c/GPG signature verification: Also look at the first GPG status line Move commit GPG signature verification to commit.c