format-patch: move message-id and related headers to the end

It is reported that GMail MSA has an undocumented limitation that
makes it reject or accept depending on some ordering of message
headers.  The current suspicion is that they want to see the
Message-Id: header near the end, so let's try moving the headers
that are related to the message-id to the end.

Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

log-tree.c

@@ -363,24 +363,27 @@ void log_write_email_headers(struct rev_info *opt, struct commit *commit,
 	const char *extra_headers = opt->extra_headers;
 	const char *name = oid_to_hex(opt->zero_commit ?
 				      &null_oid : &commit->object.oid);
+	struct strbuf message_ids = STRBUF_INIT;
 
 	*need_8bit_cte_p = 0; /* unknown */
 
 	fprintf(opt->diffopt.file, "From %s Mon Sep 17 00:00:00 2001\n", name);
 	graph_show_oneline(opt->graph);
-	if (opt->message_id) {
-		fprintf(opt->diffopt.file, "Message-Id: <%s>\n", opt->message_id);
-		graph_show_oneline(opt->graph);
-	}
+
+	if (opt->message_id)
+		strbuf_addf(&message_ids, "Message-Id: <%s>\n", opt->message_id);
+
 	if (opt->ref_message_ids && opt->ref_message_ids->nr > 0) {
 		int i, n;
 		n = opt->ref_message_ids->nr;
-		fprintf(opt->diffopt.file, "In-Reply-To: <%s>\n", opt->ref_message_ids->items[n-1].string);
+		strbuf_addf(&message_ids, "In-Reply-To: <%s>\n",
+			    opt->ref_message_ids->items[n-1].string);
 		for (i = 0; i < n; i++)
-			fprintf(opt->diffopt.file, "%s<%s>\n", (i > 0 ? "\t" : "References: "),
-			       opt->ref_message_ids->items[i].string);
-		graph_show_oneline(opt->graph);
+			strbuf_addf(&message_ids, "%s<%s>\n",
+				    (i > 0 ? "\t" : "References: "),
+				    opt->ref_message_ids->items[i].string);
 	}
+
 	if (opt->mime_boundary && maybe_multipart) {
 		static struct strbuf subject_buffer = STRBUF_INIT;
 		static struct strbuf buffer = STRBUF_INIT;
@@ -425,6 +428,17 @@ void log_write_email_headers(struct rev_info *opt, struct commit *commit,
 		opt->diffopt.stat_sep = buffer.buf;
 		strbuf_release(&filename);
 	}
+
+	if (message_ids.len) {
+		static struct strbuf buf = STRBUF_INIT;
+
+		strbuf_reset(&buf);
+		strbuf_addbuf(&buf, &message_ids);
+		if (extra_headers)
+			strbuf_addstr(&buf, extra_headers);
+		extra_headers = buf.buf;
+	}
+
 	*extra_headers_p = extra_headers;
 }