format-patch: Add a signature option (--signature)

By default, git uses the version string as the signature for all
patches output by format-patch. Many employers (mine included)
require the use of a signature on all outgoing mails. In a
format-patch | send-email workflow there isn't an easy way to modify
the signature without breaking the pipe and manually replacing the
version string with the signature required. Instead of doing all that
work, add an option (--signature) and a config variable
(format.signature) to replace the default git version signature when
formatting patches.

This does modify the original behavior of format-patch a bit. First
off the version string is now placed in the cover letter by default.
Secondly, once the configuration variable format.signature is added
to the .config file there is no way to revert back to the default
git version signature. Instead, specifying the --no-signature option
will remove the signature from the patches entirely.

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 15 insertions, 3 deletions

diff --git a/builtin/log.c b/builtin/log.c
index 976e16f9f2..f068583618 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -549,8 +549,9 @@ static void add_header(const char *value)
 
 #define THREAD_SHALLOW 1
 #define THREAD_DEEP 2
-static int thread = 0;
-static int do_signoff = 0;
+static int thread;
+static int do_signoff;
+static const char *signature = git_version_string;
 
 static int git_format_config(const char *var, const char *value, void *cb)
 {
@@ -609,6 +610,8 @@ static int git_format_config(const char *var, const char *value, void *cb)
 		do_signoff = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "format.signature"))
+		return git_config_string(&signature, var, value);
 
 	return git_log_config(var, value, cb);
 }
@@ -703,6 +706,12 @@ static void gen_message_id(struct rev_info *info, char *base)
 	info->message_id = strbuf_detach(&buf, NULL);
 }
 
+static void print_signature(void)
+{
+	if (signature && *signature)
+		printf("-- \n%s\n\n", signature);
+}
+
 static void make_cover_letter(struct rev_info *rev, int use_stdout,
 			      int numbered, int numbered_files,
 			      struct commit *origin,
@@ -796,6 +805,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	diff_flush(&opts);
 
 	printf("\n");
+	print_signature();
 }
 
 static const char *clean_message_id(const char *msg_id)
@@ -1035,6 +1045,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		{ OPTION_CALLBACK, 0, "thread", &thread, "style",
 			    "enable message threading, styles: shallow, deep",
 			    PARSE_OPT_OPTARG, thread_callback },
+		OPT_STRING(0, "signature", &signature, "signature",
+			    "add a signature"),
 		OPT_END()
 	};
 
@@ -1313,7 +1325,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 				       mime_boundary_leader,
 				       rev.mime_boundary);
 			else
-				printf("-- \n%s\n\n", git_version_string);
+				print_signature();
 		}
 		if (!use_stdout)
 			fclose(stdout);