Add signature verification of PGP/MIME-signed parts with --verify.

This is primarily for notmuch-show, although the functionality is
added to show-message.  Once signatures are processed a new
part_sigstatus formatter is emitted, and the entire multipart/signed
part is replaced with the contents of the signed part.

At the moment only a json part_sigstatus formatting function is
available.  Emacs support to follow.

The original work for this patch was done by

  Daniel Kahn Gillmor <dkg@fifthhorseman.net>

whose help with this functionality I greatly appreciate.

1 files changed, 8 insertions, 0 deletions

diff --git a/notmuch.c b/notmuch.c
index 262d677c..cd3cb1b5 100644
--- a/notmuch.c
+++ b/notmuch.c
@@ -294,6 +294,14 @@ static command_t commands[] = {
       "\t\tmessage MIME structure, and are identified in the 'json' or\n"
       "\t\t'text' output formats.\n"
       "\n"
+      "\t--verify\n"
+      "\n"
+      "\t\tCompute and report the validity of any MIME cryptographic\n"
+      "\t\tsignatures found in the selected content (ie.\n"
+      "\t\t\"multipart/signed\" parts). Status of the signature will be\n"
+      "\t\treported (currently only supported with --format=json) and\n"
+      "\t\tthe multipart/signed part will be replaced by the signed data.\n"
+      "\n"
       "\n"
       "\tA common use of \"notmuch show\" is to display a single\n"
       "\tthread of email messages. For this, use a search term of\n"