format-patch: preserve subject newlines with -k

In older versions of git, we used rfc822 header folding to
indicate that the original subject line had multiple lines
in it.  But since a1f6baa (format-patch: wrap long header
lines, 2011-02-23), we now use header folding whenever there
is a long line.

This means that "git am" cannot trust header folding as a
sign from format-patch that newlines should be preserved.
Instead, format-patch needs to signal more explicitly that
the newlines are significant.  This patch does so by
rfc2047-encoding the newlines in the subject line. No
changes are needed on the "git am" end; it already decodes
the newlines properly.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/pretty.c b/pretty.c
index 1bb7e075e..193bafd83 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1131,7 +1131,8 @@ void pp_title_line(const struct pretty_print_context *pp,
 	struct strbuf title;
 
 	strbuf_init(&title, 80);
-	*msg_p = format_subject(&title, *msg_p, " ");
+	*msg_p = format_subject(&title, *msg_p,
+				pp->preserve_subject ? "\n" : " ");
 
 	strbuf_grow(sb, title.len + 1024);
 	if (pp->subject) {