[PATCH 2/2] format-patch: allow forcing the use of in-body From: header

[Junio C Hamano <gitster@pobox.com>]

Users may be authoring and committing their commits under the same
e-mail address they use to send their patches from, in which case
they shouldn't need to use the in-body From: line in their outgoing
e-mails.  At the receiving end, "git am" will use the address on the
"From:" header of the incoming e-mail and all should be well.

Some mailing lists, however, mangle the From: address from what the
original sender had; in such an unfortunate situation, the user may
want to add the in-body "From:" header even for their own patch.

"git format-patch --[no-]force-inbody-from" was invented for such
users.

Note.  This is an uncooked early draft.  Things to think about
include (but not limited to, of course):

 * Should this rather be --use-inbody-from=yes,no,auto tristate,
   that defaults to "auto", which is the current behaviour i.e.
   "when --from is given, add it only when it does not match the
   payload".  "yes" would mean "always emit the --from address as
   in-body From:" and "no" would mean ... what?  "Ignore --from"?
   Then why is the user giving --from in the first place?

 * Should it be "inbody" or "in-body"?

 * Should it have a corresponding configuration variable?

 * Should this patch be scrapped and the feature should be done
   inside "git send-email" instead?

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/log.c           |  2 ++
 pretty.c                |  2 ++
 revision.h              |  1 +
 t/t4014-format-patch.sh | 13 +++++++++++++
 4 files changed, 18 insertions(+)

diff --git a/builtin/log.c b/builtin/log.c
index 9b937d59b8..83b2d01b49 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -1897,6 +1897,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			   N_("show changes against <refspec> in cover letter or single patch")),
 		OPT_INTEGER(0, "creation-factor", &creation_factor,
 			    N_("percentage by which creation is weighted")),
+		OPT_BOOL(0, "force-inbody-from", &rev.force_inbody_from,
+			 N_("Use in-body From: even for your own commit")),
 		OPT_END()
 	};
 
diff --git a/pretty.c b/pretty.c
index 51e3fa5736..e266208c0b 100644
--- a/pretty.c
+++ b/pretty.c
@@ -483,6 +483,8 @@ static int use_inbody_from(const struct pretty_print_context *pp, const struct i
 		return 0;
 	if (ident_cmp(pp->from_ident, ident))
 		return 1;
+	if (pp->rev && pp->rev->force_inbody_from)
+		return 1;
 	return 0;
 }
 
diff --git a/revision.h b/revision.h
index bb91e7ed91..a2d3813a21 100644
--- a/revision.h
+++ b/revision.h
@@ -208,6 +208,7 @@ struct rev_info {
 
 	/* Format info */
 	int		show_notes;
+	unsigned int	force_inbody_from;
 	unsigned int	shown_one:1,
 			shown_dashes:1,
 			show_merge:1,
diff --git a/t/t4014-format-patch.sh b/t/t4014-format-patch.sh
index fbec8ad2ef..a4ecd433e2 100755
--- a/t/t4014-format-patch.sh
+++ b/t/t4014-format-patch.sh
@@ -1400,6 +1400,19 @@ test_expect_success '--from omits redundant in-body header' '
 	test_cmp expect patch.head
 '
 
+test_expect_success 'with --force-inbody-from, --from keeps redundant in-body header' '
+	git format-patch --force-inbody-from \
+		-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 'in-body headers trigger content encoding' '
 	test_env GIT_AUTHOR_NAME="éxötìc" test_commit exotic &&
 	test_when_finished "git reset --hard HEAD^" &&
-- 
2.37.2-587-g47adba97a9