verify-tag: share code with verify-commit

verify-tag was executing an entirely different codepath than
verify-commit, except for the underlying verify_signed_buffer.  Move
much of the code from check_commit_signature to a generic
check_signature function and adjust both codepaths to call it.

Update verify-tag to explicitly output the signature text, as we now
call verify_signed_buffer with strbufs to catch the output, which
prevents it from being printed automatically.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/verify-tag.c

@@ -20,16 +20,23 @@ static const char * const verify_tag_usage[] = {
 
 static int run_gpg_verify(const char *buf, unsigned long size, int verbose)
 {
+	struct signature_check sigc;
 	int len;
 
+	memset(&sigc, 0, sizeof(sigc));
+
 	len = parse_signature(buf, size);
 	if (verbose)
 		write_in_full(1, buf, len);
 
 	if (size == len)
 		return error("no signature found");
 
-	return verify_signed_buffer(buf, len, buf + len, size - len, NULL, NULL);
+	check_signature(buf, len, buf + len, size - len, &sigc);
+	fputs(sigc.gpg_output, stderr);
+
+	signature_check_clear(&sigc);
+	return sigc.result != 'G' && sigc.result != 'U';
 }
 
 static int verify_tag(const char *name, int verbose)

commit.c

@@ -1231,27 +1231,14 @@ void check_commit_signature(const struct commit *commit, struct signature_check
 {
 	struct strbuf payload = STRBUF_INIT;
 	struct strbuf signature = STRBUF_INIT;
-	struct strbuf gpg_output = STRBUF_INIT;
-	struct strbuf gpg_status = STRBUF_INIT;
-	int status;
 
 	sigc->result = 'N';
 
 	if (parse_signed_commit(commit, &payload, &signature) <= 0)
 		goto out;
-	status = verify_signed_buffer(payload.buf, payload.len,
-				      signature.buf, signature.len,
-				      &gpg_output, &gpg_status);
-	if (status && !gpg_output.len)
-		goto out;
-	sigc->payload = strbuf_detach(&payload, NULL);
-	sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
-	sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
-	parse_gpg_output(sigc);
+	check_signature(payload.buf, payload.len, signature.buf, signature.len, sigc);
 
  out:
-	strbuf_release(&gpg_status);
-	strbuf_release(&gpg_output);
 	strbuf_release(&payload);
 	strbuf_release(&signature);
 }

gpg-interface.c

@@ -60,6 +60,29 @@ void parse_gpg_output(struct signature_check *sigc)
 	}
 }
 
+void check_signature(const char *payload, size_t plen, const char *signature,
+	size_t slen, struct signature_check *sigc)
+{
+	struct strbuf gpg_output = STRBUF_INIT;
+	struct strbuf gpg_status = STRBUF_INIT;
+	int status;
+
+	sigc->result = 'N';
+
+	status = verify_signed_buffer(payload, plen, signature, slen,
+				      &gpg_output, &gpg_status);
+	if (status && !gpg_output.len)
+		goto out;
+	sigc->payload = xmemdupz(payload, plen);
+	sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
+	sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
+	parse_gpg_output(sigc);
+
+ out:
+	strbuf_release(&gpg_status);
+	strbuf_release(&gpg_output);
+}
+
 /*
  * Look at GPG signed content (e.g. a signed tag object), whose
  * payload is followed by a detached signature on it.  Return the

gpg-interface.h

@@ -27,5 +27,7 @@ extern int verify_signed_buffer(const char *payload, size_t payload_size, const
 extern int git_gpg_config(const char *, const char *, void *);
 extern void set_signing_key(const char *);
 extern const char *get_signing_key(void);
+extern void check_signature(const char *payload, size_t plen,
+	const char *signature, size_t slen, struct signature_check *sigc);
 
 #endif