diff.c: move line ending check into emit_hunk_header

The emit_hunk_header() function is responsible for assembling a
hunk header and calling emit_line() to send the hunk header
to the output file.  Its only caller fn_out_consume() needs
to prepare for a case where the function emits an incomplete
line and add the terminating LF.

Instead make sure emit_hunk_header() to always send a
completed line to emit_line().

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -678,6 +678,8 @@ static void emit_hunk_header(struct emit_callback *ecbdata,
 	}
 
 	strbuf_add(&msgbuf, line + len, org_len - len);
+	strbuf_complete_line(&msgbuf);
+
 	emit_line(ecbdata->opt, "", "", msgbuf.buf, msgbuf.len);
 	strbuf_release(&msgbuf);
 }
@@ -1315,8 +1317,6 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 		len = sane_truncate_line(ecbdata, line, len);
 		find_lno(line, ecbdata);
 		emit_hunk_header(ecbdata, line, len);
-		if (line[len-1] != '\n')
-			putc('\n', o->file);
 		return;
 	}