verify-commit: add option to print raw gpg status information

verify-commit by default displays human-readable output on standard
error.  However, it can also be useful to get access to the raw gpg
status information, which is machine-readable, allowing automated
implementation of signing policy.  Add a --raw option to make
verify-commit produce the gpg status information on standard error
instead of the human-readable format.

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

Documentation/git-verify-commit.txt

@@ -16,6 +16,10 @@ Validates the gpg signature created by 'git commit -S'.
 
 OPTIONS
 -------
+--raw::
+	Print the raw gpg status output to standard error instead of the normal
+	human-readable output.
+
 -v::
 --verbose::
 	Print the contents of the commit object before validating it.

builtin/verify-commit.c

@@ -18,7 +18,7 @@ static const char * const verify_commit_usage[] = {
 		NULL
 };
 
-static int run_gpg_verify(const unsigned char *sha1, const char *buf, unsigned long size, int verbose)
+static int run_gpg_verify(const unsigned char *sha1, const char *buf, unsigned long size, unsigned flags)
 {
 	struct signature_check signature_check;
 	int ret;
@@ -26,13 +26,13 @@ static int run_gpg_verify(const unsigned char *sha1, const char *buf, unsigned l
 	memset(&signature_check, 0, sizeof(signature_check));
 
 	ret = check_commit_signature(lookup_commit(sha1), &signature_check);
-	print_signature_buffer(&signature_check, verbose ? GPG_VERIFY_VERBOSE : 0);
+	print_signature_buffer(&signature_check, flags);
 
 	signature_check_clear(&signature_check);
 	return ret;
 }
 
-static int verify_commit(const char *name, int verbose)
+static int verify_commit(const char *name, unsigned flags)
 {
 	enum object_type type;
 	unsigned char sha1[20];
@@ -50,7 +50,7 @@ static int verify_commit(const char *name, int verbose)
 		return error("%s: cannot verify a non-commit object of type %s.",
 				name, typename(type));
 
-	ret = run_gpg_verify(sha1, buf, size, verbose);
+	ret = run_gpg_verify(sha1, buf, size, flags);
 
 	free(buf);
 	return ret;
@@ -67,8 +67,10 @@ static int git_verify_commit_config(const char *var, const char *value, void *cb
 int cmd_verify_commit(int argc, const char **argv, const char *prefix)
 {
 	int i = 1, verbose = 0, had_error = 0;
+	unsigned flags = 0;
 	const struct option verify_commit_options[] = {
 		OPT__VERBOSE(&verbose, N_("print commit contents")),
+		OPT_BIT(0, "raw", &flags, N_("print raw gpg status output"), GPG_VERIFY_RAW),
 		OPT_END()
 	};
 
@@ -79,11 +81,14 @@ int cmd_verify_commit(int argc, const char **argv, const char *prefix)
 	if (argc <= i)
 		usage_with_options(verify_commit_usage, verify_commit_options);
 
+	if (verbose)
+		flags |= GPG_VERIFY_VERBOSE;
+
 	/* sometimes the program was terminated because this signal
 	 * was received in the process of writing the gpg input: */
 	signal(SIGPIPE, SIG_IGN);
 	while (i < argc)
-		if (verify_commit(argv[i++], verbose))
+		if (verify_commit(argv[i++], flags))
 			had_error = 1;
 	return had_error;
 }

gpg-interface.c

@@ -87,11 +87,14 @@ int check_signature(const char *payload, size_t plen, const char *signature,
 
 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
 {
+	const char *output = flags & GPG_VERIFY_RAW ?
+		sigc->gpg_status : sigc->gpg_output;
+
 	if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 		fputs(sigc->payload, stdout);
 
-	if (sigc->gpg_output)
-		fputs(sigc->gpg_output, stderr);
+	if (output)
+		fputs(output, stderr);
 }
 
 /*

gpg-interface.h

@@ -2,6 +2,7 @@
 #define GPG_INTERFACE_H
 
 #define GPG_VERIFY_VERBOSE	1
+#define GPG_VERIFY_RAW		2
 
 struct signature_check {
 	char *payload;

t/t7510-signed-commit.sh

@@ -88,6 +88,37 @@ test_expect_success GPG 'verify-commit exits success on untrusted signature' '
 	grep "not certified" actual
 '
 
+test_expect_success GPG 'verify signatures with --raw' '
+	(
+		for commit in initial second merge fourth-signed fifth-signed sixth-signed seventh-signed
+		do
+			git verify-commit --raw $commit 2>actual &&
+			grep "GOODSIG" actual &&
+			! grep "BADSIG" actual &&
+			echo $commit OK || exit 1
+		done
+	) &&
+	(
+		for commit in merge^2 fourth-unsigned sixth-unsigned seventh-unsigned
+		do
+			test_must_fail git verify-commit --raw $commit 2>actual &&
+			! grep "GOODSIG" actual &&
+			! grep "BADSIG" actual &&
+			echo $commit OK || exit 1
+		done
+	) &&
+	(
+		for commit in eighth-signed-alt
+		do
+			git verify-commit --raw $commit 2>actual &&
+			grep "GOODSIG" actual &&
+			! grep "BADSIG" actual &&
+			grep "TRUST_UNDEFINED" actual &&
+			echo $commit OK || exit 1
+		done
+	)
+'
+
 test_expect_success GPG 'show signed commit with signature' '
 	git show -s initial >commit &&
 	git show -s --show-signature initial >show &&