[PATCH 7/8] gpg-interface: introduce new signature format "X509" using gpgsm

[Henning Schild <henning.schild@siemens.com>]

This commit allows git to create and check X509 type signatures using
gpgsm.

Signed-off-by: Henning Schild <henning.schild@siemens.com>
---
 Documentation/config.txt |  5 ++++-
 gpg-interface.c          | 10 +++++++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index c88903399..337df6e48 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1828,9 +1828,12 @@ gpg.program::
 	signed, and the program is expected to send the result to its
 	standard output.
 
+gpg.programX509::
+	Just like gpg.program, here the default you override is "`gpgsm`".
+
 gpg.format::
 	Specifies which key format to use when signing with `--gpg-sign`.
-	Default is "PGP", that is also the only supported value.
+	Default is "PGP" and another possible value is "X509".
 
 gui.commitMsgWidth::
 	Defines how wide the commit message window is in the
diff --git a/gpg-interface.c b/gpg-interface.c
index aa747278e..85d721007 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -16,13 +16,18 @@ struct gpg_format_data {
 
 #define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"
 #define PGP_MESSAGE "-----BEGIN PGP MESSAGE-----"
+#define X509_SIGNATURE "-----BEGIN SIGNED MESSAGE-----"
 
-enum gpgformats { PGP_FMT };
+enum gpgformats { PGP_FMT, X509_FMT };
 struct gpg_format_data gpg_formats[] = {
 	{ .format = "PGP", .program = "gpg",
 	  .extra_args_verify = { "--keyid-format=long", },
 	  .sigs = { PGP_SIGNATURE, PGP_MESSAGE, },
 	},
+	{ .format = "X509", .program = "gpgsm",
+	  .extra_args_verify = { NULL },
+	  .sigs = {X509_SIGNATURE, NULL, }
+	},
 };
 static const char *gpg_format = "PGP";
 
@@ -190,6 +195,9 @@ int git_gpg_config(const char *var, const char *value, void *cb)
 	if (!strcmp(var, "gpg.program"))
 		return git_config_string(&gpg_formats[PGP_FMT].program, var,
 					 value);
+	if (!strcmp(var, "gpg.programX509"))
+		return git_config_string(&gpg_formats[X509_FMT].program, var,
+					 value);
 	return 0;
 }
 
-- 
2.16.4