format-patch: add "--signature-file=<file>" option

Add an option to format-patch for reading a signature from a file.

  $ git format-patch -1 --signature-file=$HOME/.signature

The config variable `format.signaturefile` can also be used to make
this the default.

  $ git config format.signaturefile $HOME/.signature

  $ git format-patch -1

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -1114,6 +1114,10 @@ format.signature::
 	Set this variable to the empty string ("") to suppress
 	signature generation.
 
+format.signaturefile::
+	Works just like format.signature except the contents of the
+	file specified by this variable will be used as the signature.
+
 format.suffix::
 	The default for format-patch is to output files with the suffix
 	`.patch`. Use this variable to change that suffix (make sure to

Documentation/git-format-patch.txt

@@ -14,6 +14,7 @@ SYNOPSIS
 		   [(--attach|--inline)[=<boundary>] | --no-attach]
 		   [-s | --signoff]
 		   [--signature=<signature> | --no-signature]
+		   [--signature-file=<file>]
 		   [-n | --numbered | -N | --no-numbered]
 		   [--start-number <n>] [--numbered-files]
 		   [--in-reply-to=Message-Id] [--suffix=.<sfx>]
@@ -233,6 +234,9 @@ configuration options in linkgit:git-notes[1] to use this workflow).
 	signature option is omitted the signature defaults to the Git version
 	number.
 
+--signature-file=<file>::
+	Works just like --signature except the signature is read from a file.
+
 --suffix=.<sfx>::
 	Instead of using `.patch` as the suffix for generated
 	filenames, use specified suffix.  A common alternative is

builtin/log.c

@@ -673,6 +673,7 @@ static void add_header(const char *value)
 static int thread;
 static int do_signoff;
 static const char *signature = git_version_string;
+static const char *signature_file;
 static int config_cover_letter;
 
 enum {
@@ -742,6 +743,8 @@ static int git_format_config(const char *var, const char *value, void *cb)
 	}
 	if (!strcmp(var, "format.signature"))
 		return git_config_string(&signature, var, value);
+	if (!strcmp(var, "format.signaturefile"))
+		return git_config_pathname(&signature_file, var, value);
 	if (!strcmp(var, "format.coverletter")) {
 		if (value && !strcasecmp(value, "auto")) {
 			config_cover_letter = COVER_AUTO;
@@ -1235,6 +1238,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			    PARSE_OPT_OPTARG, thread_callback },
 		OPT_STRING(0, "signature", &signature, N_("signature"),
 			    N_("add a signature")),
+		OPT_FILENAME(0, "signature-file", &signature_file,
+				N_("add a signature from a file")),
 		OPT__QUIET(&quiet, N_("don't print the patch filenames")),
 		OPT_END()
 	};
@@ -1452,6 +1457,18 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			cover_letter = (config_cover_letter == COVER_ON);
 	}
 
+	if (!signature) {
+		; /* --no-signature inhibits all signatures */
+	} else if (signature && signature != git_version_string) {
+		; /* non-default signature already set */
+	} else if (signature_file) {
+		struct strbuf buf = STRBUF_INIT;
+
+		if (strbuf_read_file(&buf, signature_file, 128) < 0)
+			die_errno(_("unable to read signature file '%s'"), signature_file);
+		signature = strbuf_detach(&buf, NULL);
+	}
+
 	if (in_reply_to || thread || cover_letter)
 		rev.ref_message_ids = xcalloc(1, sizeof(struct string_list));
 	if (in_reply_to) {

t/t4014-format-patch.sh

@@ -762,6 +762,67 @@ test_expect_success 'format-patch --signature="" suppresses signatures' '
 	! grep "^-- \$" output
 '
 
+test_expect_success 'prepare mail-signature input' '
+	cat >mail-signature <<-\EOF
+
+	Test User <test.email@kernel.org>
+	http://git.kernel.org/cgit/git/git.git
+
+	git.kernel.org/?p=git/git.git;a=summary
+
+	EOF
+'
+
+test_expect_success '--signature-file=file works' '
+	git format-patch --stdout --signature-file=mail-signature -1 >output &&
+	check_patch output &&
+	sed -e "1,/^-- \$/d" <output >actual &&
+	{
+		cat mail-signature && echo
+	} >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'format.signaturefile works' '
+	test_config format.signaturefile mail-signature &&
+	git format-patch --stdout -1 >output &&
+	check_patch output &&
+	sed -e "1,/^-- \$/d" <output >actual &&
+	{
+		cat mail-signature && echo
+	} >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '--no-signature suppresses format.signaturefile ' '
+	test_config format.signaturefile mail-signature &&
+	git format-patch --stdout --no-signature -1 >output &&
+	check_patch output &&
+	! grep "^-- \$" output
+'
+
+test_expect_success '--signature-file overrides format.signaturefile' '
+	cat >other-mail-signature <<-\EOF
+	Use this other signature instead of mail-signature.
+	EOF
+	test_config format.signaturefile mail-signature &&
+	git format-patch --stdout \
+			--signature-file=other-mail-signature -1 >output &&
+	check_patch output &&
+	sed -e "1,/^-- \$/d" <output >actual &&
+	{
+		cat other-mail-signature && echo
+	} >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '--signature overrides format.signaturefile' '
+	test_config format.signaturefile mail-signature &&
+	git format-patch --stdout --signature="my sig" -1 >output &&
+	check_patch output &&
+	grep "my sig" output
+'
+
 test_expect_success TTY 'format-patch --stdout paginates' '
 	rm -f pager_used &&
 	test_terminal env GIT_PAGER="wc >pager_used" git format-patch --stdout --all &&