format-patch: learn format.forceInBodyFrom configuration variable

As the need to use the "--force-in-body-from" option primarily is
tied to which mailing list the mails go to (and get their From:
address mangled), it is likely that a user who needs to use this
option once to interact with their upstream project needs to use it
for all patches they send out.

Add a configuration variable, suitable for setting in the local
configuration file per repository, for this.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/format.txt

@@ -15,6 +15,10 @@ format.from::
 	different.  If set to a non-boolean value, format-patch uses that
 	value instead of your committer identity.  Defaults to false.
 
+format.forceInBodyFrom::
+	Provides the default value for the `--[no-]force-in-body-from`
+	option to format-patch.  Defaults to false.
+
 format.numbered::
 	A boolean which can enable or disable sequence numbers in patch
 	subjects.  It defaults to "auto" which enables it only if there

Documentation/git-format-patch.txt

@@ -283,6 +283,8 @@ feeding the result to `git send-email`.
 	the in-body "From:" is added even when the sender and the
 	author have the same name and address, which may help if the
 	mailing list software mangles the sender's identity.
+	Defaults to the value of the `format.forceInBodyFrom`
+	configuration variable.
 
 --add-header=<header>::
 	Add an arbitrary header to the email headers.  This is in addition

builtin/log.c

@@ -1007,6 +1007,10 @@ static int git_format_config(const char *var, const char *value, void *cb)
 			from = NULL;
 		return 0;
 	}
+	if (!strcmp(var, "format.forceinbodyfrom")) {
+		force_in_body_from = git_config_bool(var, value);
+		return 0;
+	}
 	if (!strcmp(var, "format.notes")) {
 		int b = git_parse_maybe_bool(value);
 		if (b < 0)

t/t4014-format-patch.sh

@@ -1413,6 +1413,30 @@ test_expect_success 'with --force-in-body-from, redundant in-body from is kept'
 	test_cmp expect patch.head
 '
 
+test_expect_success 'format.forceInBodyFrom, equivalent to --force-in-body-from' '
+	git -c format.forceInBodyFrom=yes format-patch \
+		-1 --stdout --from="A U Thor <author@example.com>" >patch &&
+	cat >expect <<-\EOF &&
+	From: A U Thor <author@example.com>
+
+	From: A U Thor <author@example.com>
+
+	EOF
+	sed -ne "/^From:/p; /^$/p; /^---$/q" patch >patch.head &&
+	test_cmp expect patch.head
+'
+
+test_expect_success 'format.forceInBodyFrom, equivalent to --force-in-body-from' '
+	git -c format.forceInBodyFrom=yes format-patch --no-force-in-body-from \
+		-1 --stdout --from="A U Thor <author@example.com>" >patch &&
+	cat >expect <<-\EOF &&
+	From: A U Thor <author@example.com>
+
+	EOF
+	sed -ne "/^From:/p; /^$/p; /^---$/q" patch >patch.head &&
+	test_cmp expect patch.head
+'
+
 test_expect_success 'in-body headers trigger content encoding' '
 	test_env GIT_AUTHOR_NAME="éxötìc" test_commit exotic &&
 	test_when_finished "git reset --hard HEAD^" &&