range-diff: output `## Notes ##` header

When notes were included in the output of range-diff, they were just
mashed together with the rest of the commit message. As a result, users
wouldn't be able to clearly distinguish where the commit message ended
and where the notes started.

Output a `## Notes ##` header when notes are detected so that notes can
be compared more clearly.

Note that we handle case of `Notes (<ref>): -> ## Notes (<ref>) ##` with
this code as well. We can't test this in this patch, however, since
there is currently no way to pass along different notes refs to `git
log`. This will be fixed in a future patch.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/range-diff.c b/range-diff.c
index 7fed5a3..6233972 100644
--- a/range-diff.c
+++ b/range-diff.c
@@ -144,6 +144,12 @@ static int read_patches(const char *range, struct string_list *list)
 				strbuf_addstr(&buf, line);
 				strbuf_addstr(&buf, "\n\n");
 				strbuf_addstr(&buf, " ## Commit message ##\n");
+			} else if (starts_with(line, "Notes") &&
+				   line[strlen(line) - 1] == ':') {
+				strbuf_addstr(&buf, "\n\n");
+				/* strip the trailing colon */
+				strbuf_addf(&buf, " ## %.*s ##\n",
+					    (int)(strlen(line) - 1), line);
 			} else if (starts_with(line, "    ")) {
 				p = line + len - 2;
 				while (isspace(*p) && p >= line)